Added internal API getMaxConnectedAudioDevices()

The API can be used to obtain the maximum number of connected
devices for A2DP or HFP.

Test: Manual
Bug: 64767509

Change-Id: Ide01ea91bc9708b20c78266d791d4775be3f943d
diff --git a/binder/android/bluetooth/IBluetooth.aidl b/binder/android/bluetooth/IBluetooth.aidl
index b446ff3..90c34b0 100644
--- a/binder/android/bluetooth/IBluetooth.aidl
+++ b/binder/android/bluetooth/IBluetooth.aidl
@@ -80,6 +80,7 @@
     boolean fetchRemoteUuids(in BluetoothDevice device);
     boolean sdpSearch(in BluetoothDevice device, in ParcelUuid uuid);
     int getBatteryLevel(in BluetoothDevice device);
+    int getMaxConnectedAudioDevices();
 
     boolean setPin(in BluetoothDevice device, boolean accept, int len, in byte[] pinCode);
     boolean setPasskey(in BluetoothDevice device, boolean accept, int len, in byte[]