Limit Max Bitpool value to SPEC recommended one

Preferred bipool for 44.1 KHz sampling rate for SBC
codec is considered as 53. Hence limit Max Bitpool
value to 53 in setconfig request to have it same as
the one DUT sets in getConfig response and in encoding
pcm packets.
few BMW series of CKs does not connect unless DUT
configures max bitpool in setconfig request to 53.

Change-Id: Ie7ca504c23f6bae8fda997cdeb3e0ff0733defb0