AVRCP: Fix not handling commands while browsing is connecting
AVRCP: Fix not handling commands while browsing is connecting

With introdution of browsing channel the .init callback is called when
browsing channel connection completes, but in the meantime the remote
device can send commands over control channel.

To fix this the init callaback of control and browsing channel are now
separated into .init_control and .init_browsing so the handler can be
register as soon the respective channel connection completes.

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