Bluetooth: Add Get socket option for L2CAP socket

- Introduce get socket option to get the congestion
  status of L2CAP socket.

- Congestion status decided based on congestion level
   at BT-IF layer and L2CAP level.

- This option is introduced for Rfcomm socket also.

CRs-Fixed: 790313
Change-Id: I73f13714bde30f7c268d6304026d4b03cbdbcfbe
4 files changed