Synchronize hl data operations

Use Case: BT crash seen while transferring data
using HDP APP to remote health device.

Steps:
1. Pair with HDP device
2. Run HDP APP and transfer data to Remote HDP device.

Failure: BT automatically resets and recovers.

Root Cause: Synchronize BITF HL free buffer as simultaneously
free buffer from BTIF and BTU thread lead to sigabort.

Fix: Validate Tx packet before memcpy as it can be free
from different thread.

Test: mm -j8
Change-Id: I566f62ce02c8e95c9f4b8d7155132e4434657f66