Allocate buffer for AV SDP in Stack

Remove buffer allocation in BTA while going for SDP before triggering
A2DP connection. This strategy is followed to address memory corruption
issues due to freeing of BTA buffer before SDP RSP call back is
triggered and access the freed buffer from there, leads to crash when
running Codemonicom tests.

The change allocates and frees buffer in stack.

Change-Id: If6d60d2aa60d19ce5120dd38c2f365d70943db81