core,voice: remove explicit "NO CARRIER" response matching

This response is already managed by the generic AT serial port and translates
it into a proper error. This change also avoids the Call.Start() call to report
a timeout in the serial port, instead we get a proper no-carrier error.

Before:

    $ sudo mmcli -m 0 --voice-create-call="number=12345678"
    Successfully created new call:
	    /org/freedesktop/ModemManager1/Call/1 outgoing (unknown)
    $ sudo mmcli -o 1 --start
    error: couldn't start the call: 'GDBus.Error:org.freedesktop.ModemManager1.Error.Serial.ResponseTimeout: Serial command timed out'

After:

    $ sudo mmcli -m 0 --voice-create-call="number=12345678"
    Successfully created new call:
	    /org/freedesktop/ModemManager1/Call/1 outgoing (unknown)
    $ sudo mmcli -o 1 --start
    error: couldn't start the call: 'GDBus.Error:org.freedesktop.ModemManager1.Error.Connection.NoCarrier: No carrier'

src/mm-broadband-modem.c

@@ -6328,15 +6328,6 @@ clip_received (MMPortSerialAt *port,
     }
 }
 
-static void
-nocarrier_received (MMPortSerialAt *port,
-                    GMatchInfo *info,
-                    MMBroadbandModem *self)
-{
-    mm_dbg ("No carrier");
-    mm_iface_modem_voice_network_hangup (MM_IFACE_MODEM_VOICE (self));
-}
-
 static void
 set_voice_unsolicited_events_handlers (MMIfaceModemVoice *self,
                                        gboolean enable,
@@ -6345,7 +6336,6 @@ set_voice_unsolicited_events_handlers (MMIfaceModemVoice *self,
 {
     GSimpleAsyncResult *result;
     MMPortSerialAt *ports[2];
-    GRegex *nocarrier_regex;
     GRegex *cring_regex;
     GRegex *ring_regex;
     GRegex *clip_regex;
@@ -6356,7 +6346,6 @@ set_voice_unsolicited_events_handlers (MMIfaceModemVoice *self,
                                         user_data,
                                         set_voice_unsolicited_events_handlers);
 
-    nocarrier_regex = mm_voice_nocarrier_regex_get ();
     cring_regex = mm_voice_cring_regex_get ();
     ring_regex  = mm_voice_ring_regex_get ();
     clip_regex  = mm_voice_clip_regex_get ();
@@ -6390,12 +6379,6 @@ set_voice_unsolicited_events_handlers (MMIfaceModemVoice *self,
             enable ? (MMPortSerialAtUnsolicitedMsgFn) clip_received : NULL,
             enable ? self : NULL,
             NULL);
-        mm_port_serial_at_add_unsolicited_msg_handler (
-            ports[i],
-            nocarrier_regex,
-            enable ? (MMPortSerialAtUnsolicitedMsgFn) nocarrier_received : NULL,
-            enable ? self : NULL,
-            NULL);
     }
 
     g_regex_unref (cring_regex);

src/mm-modem-helpers.c

@@ -361,18 +361,6 @@ mm_voice_clip_regex_get (void)
                         NULL);
 }
 
-GRegex *
-mm_voice_nocarrier_regex_get (void)
-{
-    /* Example:
-     * <CR><LF>NO CARRIER<CR><LF>
-     */
-    return g_regex_new ("\\r\\n\\NO CARRIER\\r\\n",
-                        G_REGEX_RAW | G_REGEX_OPTIMIZE,
-                        0,
-                        NULL);
-}
-
 /*************************************************************************/
 
 /* +CREG: <stat>                      (GSM 07.07 CREG=1 unsolicited) */

src/mm-modem-helpers.h

@@ -88,7 +88,6 @@ GArray *mm_filter_supported_capabilities (MMModemCapability all,
 GRegex *mm_voice_ring_regex_get (void);
 GRegex *mm_voice_cring_regex_get(void);
 GRegex *mm_voice_clip_regex_get (void);
-GRegex *mm_voice_nocarrier_regex_get (void);
 
 /*****************************************************************************/
 /* 3GPP specific helpers and utilities */