Nitrous: Add BTBCM LPM logger for debugging issue

Recording useful debug messages and cache into a logbuffer for the
purpose of dumming the log via device node dev/logbuffer_btlpm once
BtHal detects errors.

Bug: 177794127
Test: BT ON, pair with a BT headset and check collected log from
Bluetooth debuggle HAL

Change-Id: I3e4006b4b4e959719e6cbcaf874264f9ca45ef42
Signed-off-by: jonerlin <jonerlin@google.com>