radio-settings: handling of dual mode technology preference

Handled two new dual mode technology preferences
"umts,gsm" and "lte,umts".
diff --git a/src/radio-settings.c b/src/radio-settings.c
index 7fd92df..7283aa9 100644
--- a/src/radio-settings.c
+++ b/src/radio-settings.c
@@ -71,9 +71,15 @@
 		return "umts";
 	case OFONO_RADIO_ACCESS_MODE_LTE:
 		return "lte";
-	default:
-		return NULL;
 	}
+
+	if (m == (OFONO_RADIO_ACCESS_MODE_UMTS|OFONO_RADIO_ACCESS_MODE_GSM))
+		return "umts,gsm";
+
+	if (m == (OFONO_RADIO_ACCESS_MODE_LTE|OFONO_RADIO_ACCESS_MODE_UMTS))
+		return "lte,umts";
+
+	return NULL;
 }
 
 static gboolean radio_access_mode_from_string(const char *str,
@@ -92,6 +98,12 @@
 	} else if (g_str_equal(str, "lte")) {
 		*mode = OFONO_RADIO_ACCESS_MODE_LTE;
 		return TRUE;
+	} else if (g_str_equal(str, "umts,gsm")) {
+		*mode = OFONO_RADIO_ACCESS_MODE_UMTS|OFONO_RADIO_ACCESS_MODE_GSM;
+		return TRUE;
+	} else if (g_str_equal(str, "lte,umts")) {
+		*mode = OFONO_RADIO_ACCESS_MODE_LTE|OFONO_RADIO_ACCESS_MODE_UMTS;
+		return TRUE;
 	}
 
 	return FALSE;