AP_GPS: added GPS_DRV_OPTIONS bit for forcing ublox GPS to 115200

this may help with some GPS modules

libraries/AP_GPS/AP_GPS.cpp

@@ -650,6 +650,9 @@ void AP_GPS::detect_instance(uint8_t instance)
                 // link to the flight controller
                 static const char blob[] = UBLOX_SET_BINARY_460800;
                 send_blob_start(instance, blob, sizeof(blob));
+            } else if (_type[instance] == GPS_TYPE_UBLOX && (_driver_options & AP_GPS_Backend::DriverOptions::UBX_Use115200)) {
+                static const char blob[] = UBLOX_SET_BINARY_115200;
+                send_blob_start(instance, blob, sizeof(blob));
             } else {
                 send_blob_start(instance, _initialisation_blob, sizeof(_initialisation_blob));
             }
@@ -674,6 +677,7 @@ void AP_GPS::detect_instance(uint8_t instance)
         if ((_type[instance] == GPS_TYPE_AUTO ||
              _type[instance] == GPS_TYPE_UBLOX) &&
             ((!_auto_config && _baudrates[dstate->current_baud] >= 38400) ||
+             (_baudrates[dstate->current_baud] >= 115200 && (_driver_options & AP_GPS_Backend::DriverOptions::UBX_Use115200)) ||
              _baudrates[dstate->current_baud] == 230400) &&
             AP_GPS_UBLOX::_detect(dstate->ublox_detect_state, data)) {
             new_gps = new AP_GPS_UBLOX(*this, state[instance], _port[instance], GPS_ROLE_NORMAL);

libraries/AP_GPS/GPS_Backend.h

@@ -85,8 +85,9 @@ public:
     }
 
     enum DriverOptions : int16_t {
-        UBX_MBUseUart2    = (1 << 0U),
-        SBF_UseBaseForYaw = (1 << 1U),
+        UBX_MBUseUart2    = (1U << 0U),
+        SBF_UseBaseForYaw = (1U << 1U),
+        UBX_Use115200     = (1U << 2U),
     };
 
 protected: