android/gatt: Add suport for server MTU changed callback
android/gatt: Add suport for server MTU changed callback

When MTU is exchange notification is send with updated MTU.
For BR/EDR notification is always send after connection.

mapfau/bluez,ComputeCycles/bluez,ComputeCycles/bluez,mapfau/bluez,pkarasev3/bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez,ComputeCycles/bluez,silent-snowman/bluez,pkarasev3/bluez,pkarasev3/bluez,silent-snowman/bluez,ComputeCycles/bluez,mapfau/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez