base-modem: separate method to lookup exact port by name

There's no point in returning a list of all ports with a given name,
just provide a lookup method that returns the single port with the
given name.

plugins/huawei/mm-broadband-modem-huawei.c

@@ -177,8 +177,7 @@ mm_broadband_modem_huawei_get_at_port_list (MMBroadbandModemHuawei *self)
     /* Additional cdc-wdm ports used for dialing */
     cdc_wdm_at_ports = mm_base_modem_find_ports (MM_BASE_MODEM (self),
                                                  MM_PORT_SUBSYS_USBMISC,
-                                                 MM_PORT_TYPE_AT,
-                                                 NULL);
+                                                 MM_PORT_TYPE_AT);
 
     return g_list_concat (out, cdc_wdm_at_ports);
 }
@@ -2201,8 +2200,7 @@ peek_port_at_for_data (MMBroadbandModemHuawei *self,
     /* Find the CDC-WDM port on the same USB interface as the given net port */
     cdc_wdm_at_ports = mm_base_modem_find_ports (MM_BASE_MODEM (self),
                                                  MM_PORT_SUBSYS_USBMISC,
-                                                 MM_PORT_TYPE_AT,
-                                                 NULL);
+                                                 MM_PORT_TYPE_AT);
     for (l = cdc_wdm_at_ports; l && !found; l = g_list_next (l)) {
         const gchar  *wdm_port_parent_path;
 

plugins/qcom-soc/mm-broadband-modem-qmi-qcom-soc.c

@@ -81,8 +81,7 @@ peek_port_qmi_for_data (MMBroadbandModemQmi  *self,
     /* Find one QMI port, we don't care which one */
     rpmsg_qmi_ports = mm_base_modem_find_ports (MM_BASE_MODEM (self),
                                                 MM_PORT_SUBSYS_RPMSG,
-                                                MM_PORT_TYPE_QMI,
-                                                NULL);
+                                                MM_PORT_TYPE_QMI);
     if (!rpmsg_qmi_ports) {
         g_set_error (error,
                      MM_CORE_ERROR,