Fix BluetoothSerial thinking it's disconnected (espressif#7372)

Currently, if a second connection occur in Bluetooth, this second connection is automatically disconnected (line 284).
This disconnection trigger the ESP_SPP_CLOSE_EVT, which clear the bit SPP_CONNECTED.
But the first connection remain active, and this flag shouldn't be cleared.

This fix the issue, by clearing the flag only if the last connection is closed

Co-authored-by: Rodrigo Garcia <rodrigo.garcia@espressif.com>

Author: aridet

libraries/BluetoothSerial/src/BluetoothSerial.cpp

@@ -301,8 +301,8 @@ static void esp_spp_cb(esp_spp_cb_event_t event, esp_spp_cb_param_t *param)
                 xEventGroupSetBits(_spp_event_group, SPP_DISCONNECTED);
                 xEventGroupSetBits(_spp_event_group, SPP_CONGESTED);
                 xEventGroupSetBits(_spp_event_group, SPP_CLOSED);
+                xEventGroupClearBits(_spp_event_group, SPP_CONNECTED);
             }        
-            xEventGroupClearBits(_spp_event_group, SPP_CONNECTED);
         } else {
             log_e("ESP_SPP_CLOSE_EVT failed!, status:%d", param->close.status);
         }