at-serial-port: allow sending 'raw' commands

Commands treated as 'raw' won't get the 'AT' prefix and will also not get the
trailing carriage return.

plugins/huawei/mm-plugin-huawei.c

@@ -213,6 +213,7 @@ huawei_custom_init_step (HuaweiCustomInitContext *ctx)
             ctx->port,
             "AT^CURC=0",
             3,
+            FALSE, /* raw */
             ctx->cancellable,
             (MMAtSerialResponseFn)curc_ready,
             ctx);
@@ -232,6 +233,7 @@ huawei_custom_init_step (HuaweiCustomInitContext *ctx)
             ctx->port,
             "AT^GETPORTMODE",
             3,
+            FALSE, /* raw */
             ctx->cancellable,
             (MMAtSerialResponseFn)getportmode_ready,
             ctx);

plugins/longcheer/mm-plugin-longcheer.c

@@ -130,6 +130,7 @@ longcheer_custom_init_step (LongcheerCustomInitContext *ctx)
         ctx->port,
         "AT+GMR",
         3,
+        FALSE, /* raw */
         ctx->cancellable,
         (MMAtSerialResponseFn)gmr_ready,
         ctx);

plugins/sierra/mm-plugin-sierra.c

@@ -124,6 +124,7 @@ sierra_custom_init_step (SierraCustomInitContext *ctx)
         ctx->port,
         "AT+GCAP",
         3,
+        FALSE, /* raw */
         ctx->cancellable,
         (MMAtSerialResponseFn)gcap_ready,
         ctx);

plugins/x22x/mm-plugin-x22x.c

@@ -129,6 +129,7 @@ x22x_custom_init_step (X22xCustomInitContext *ctx)
         ctx->port,
         "AT+GMR",
         3,
+        FALSE, /* raw */
         ctx->cancellable,
         (MMAtSerialResponseFn)gmr_ready,
         ctx);