Bluetooth: RFCOMM: Implement timer in dlc

This basically implements timer for connection and disconnection.

Conn timer will be started when dlc is initialized and stopped
when it is connected. Authentication if any, will be also included
in this timer.

Disc timer will be started during disconnect initiation.

Change-Id: Ia4b74e478fefa42db21aef528e623a24c72ddf7f
Signed-off-by: Jaganath Kanakkassery <jaganathx.kanakkassery@intel.com>