audio:hal: Fix compilation error on a2dp.c

-Compilation error is seen on LE build in a2dp.c as LE uses
 older version of BT split A2DP structures.
-Used LE compilation flag to mask out LA specific changes.

CRs-Fixed: 2153541
Change-Id: Id7bfacc46f1effca56e97dc2510cf69a9620580d