AP_GPS: fixed UAVCAN as 2nd GPS

This fixes the issue here:

  https://discuss.ardupilot.org/t/ac3-6-dev-dual-gps-issues/19172

thanks to Francisco for spotting the issue

this is tested with UAVCAN as 2nd GPS, ublox as primary

libraries/AP_GPS/AP_GPS.cpp

@@ -399,6 +399,11 @@ void AP_GPS::detect_instance(uint8_t instance)
     struct detect_state *dstate = &detect_state[instance];
     uint32_t now = AP_HAL::millis();
 
+    state[instance].instance = instance;
+    state[instance].status = NO_GPS;
+    state[instance].hdop = GPS_UNKNOWN_DOP;
+    state[instance].vdop = GPS_UNKNOWN_DOP;
+
     switch (_type[instance]) {
 #if CONFIG_HAL_BOARD == HAL_BOARD_QURT
     case GPS_TYPE_QURT:
@@ -456,11 +461,6 @@ void AP_GPS::detect_instance(uint8_t instance)
         return;
     }
 
-    state[instance].instance = instance;
-    state[instance].status = NO_GPS;
-    state[instance].hdop = GPS_UNKNOWN_DOP;
-    state[instance].vdop = GPS_UNKNOWN_DOP;
-
     // all remaining drivers automatically cycle through baud rates to detect
     // the correct baud rate, and should have the selected baud broadcast
     dstate->auto_detected_baud = true;