GATT: Expose opportunistic client API to Java

* Opportunistic GATT connection allows system service to subscribe to
  characteristic notifications without holding the BLE connection
* Exposing this flag to Java allows Android applications to use it

Bug: 35874078
Test: make, test on Android App
Change-Id: If4683b2281d743dacdece6b08db49ec539af3b18
diff --git a/include/hardware/bt_gatt_client.h b/include/hardware/bt_gatt_client.h
index 9adeb6f..cafc2da 100644
--- a/include/hardware/bt_gatt_client.h
+++ b/include/hardware/bt_gatt_client.h
@@ -207,7 +207,8 @@
 
     /** Create a connection to a remote LE or dual-mode device */
     bt_status_t (*connect)(int client_if, const RawAddress& bd_addr,
-                           bool is_direct, int transport, int initiating_phys);
+                           bool is_direct, int transport, bool opportunistic,
+                           int initiating_phys);
 
     /** Disconnect a remote device or cancel a pending connection */
     bt_status_t (*disconnect)( int client_if, const RawAddress& bd_addr,