android/gatt: Remove device's connection counter
android/gatt: Remove device's connection counter

Originally we used connection counter to determine if device object
is still needed or should be destroyed but we switched to reference
counting quite some time ago and this counter is not needed anymore.

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