mm-modem-helpers.c: adjust the RING regex

The Broadmobi BM818 has some additional carriage returns in the RING message

Fixes: #626

Signed-off-by: Angus Ainslie <angus@akkea.ca>

src/mm-modem-helpers.c

@@ -460,7 +460,7 @@ mm_voice_ring_regex_get (void)
     /* Example:
      * <CR><LF>RING<CR><LF>
      */
-    return g_regex_new ("\\r\\nRING\\r\\n",
+    return g_regex_new ("\\r\\nRING(?:\\r)?\\r\\n",
                         G_REGEX_RAW | G_REGEX_OPTIMIZE,
                         0,
                         NULL);