Bluetooth: Added function prototype for codec.

This function is used to notify the BT APP
about the codec negtiated.

Change-Id: I058a9b6409341d3fc849de1386174207bd9df1e3
(cherry picked from commit cce5c76bfa42c54e15d6eb3bd43ae9cea82c462c)
(cherry picked from commit 3add2cdff0fd82f887925ff6f26211c8ee6d0c07)
(cherry picked from commit ed834a7088edaa64aa48912abf15cc6ae510d766)