base-modem-at: switch to use the MMIfacePortAt by default

The whole codebase is updated to assume the MMBaseModem AT operations
require an object implementing the MMIfacePortAt interface, instead of
a MMPortSerialAt object.

In the places where we know the port is a MMPortSerialAt, e.g. when we
query explicitly for the primary or secondary serial AT port, we will
use an explicit MM_IFACE_PORT_AT() cast when calling the AT command
method.

In the places where we get_best_at_port() we're going to assume that
we don't know the port type. This method will be updated in a follow
up commit to support the MMIfacePortAt interface as well.

src/plugins/cinterion/mm-broadband-bearer-cinterion.c

@@ -359,7 +359,7 @@ handle_cancel_dial (GTask *task)
     command = g_strdup_printf ("^SWWAN=0,%u,%u",
                                ctx->cid, usb_interface_configs[ctx->usb_interface_config_index].swwan_index);
     mm_base_modem_at_command_full (ctx->modem,
-                                   ctx->primary,
+                                   MM_IFACE_PORT_AT (ctx->primary),
                                    command,
                                    3,
                                    FALSE,
@@ -409,7 +409,7 @@ dial_3gpp_context_step (GTask *task)
             /* Send SGAUTH write, if User & Pass are provided.
              * advance to next state by callback */
             mm_base_modem_at_command_full (ctx->modem,
-                                           ctx->primary,
+                                           MM_IFACE_PORT_AT (ctx->primary),
                                            command,
                                            10,
                                            FALSE,
@@ -435,7 +435,7 @@ dial_3gpp_context_step (GTask *task)
 
         if (default_swwan_behavior) {
             mm_base_modem_at_command_full (ctx->modem,
-                                           ctx->primary,
+                                           MM_IFACE_PORT_AT (ctx->primary),
                                            command,
                                            MM_BASE_BEARER_DEFAULT_CONNECTION_TIMEOUT,
                                            FALSE,
@@ -451,7 +451,7 @@ dial_3gpp_context_step (GTask *task)
          * we'll mark the bearer disconnected later in the callback.
          */
         mm_base_modem_at_command_full (ctx->modem,
-                                       ctx->primary,
+                                       MM_IFACE_PORT_AT (ctx->primary),
                                        command,
                                        MM_BASE_BEARER_DEFAULT_CONNECTION_TIMEOUT,
                                        FALSE,
@@ -652,7 +652,7 @@ disconnect_3gpp_context_step (GTask *task)
         mm_obj_dbg (self, "disconnect step %u/%u: disconnecting PDP CID %u...",
                     ctx->step, DISCONNECT_3GPP_CONTEXT_STEP_LAST, ctx->cid);
         mm_base_modem_at_command_full (ctx->modem,
-                                       ctx->primary,
+                                       MM_IFACE_PORT_AT (ctx->primary),
                                        command,
                                        MM_BASE_BEARER_DEFAULT_DISCONNECTION_TIMEOUT,
                                        FALSE,

src/plugins/cinterion/mm-broadband-modem-cinterion.c

@@ -730,7 +730,7 @@ modem_power_off (MMIfaceModem        *self,
      * fires */
     g_assert (MAX_POWER_OFF_WAIT_TIME_SECS > 5);
     mm_base_modem_at_command_full (MM_BASE_MODEM (self),
-                                   ctx->primary,
+                                   MM_IFACE_PORT_AT (ctx->primary),
                                    "^SMSO",
                                    5,
                                    FALSE, /* allow_cached */

src/plugins/cinterion/mm-shared-cinterion.c

@@ -988,7 +988,7 @@ run_voice_enable_disable_unsolicited_events (GTask *task)
 
     if (port) {
         mm_base_modem_at_command_full (MM_BASE_MODEM (self),
-                                       port,
+                                       MM_IFACE_PORT_AT (port),
                                        ctx->slcc_command,
                                        3,
                                        FALSE,