ASoC: compress: Update lock for dpcm calls

Compress driver calls into the dpcm framework when
usecase is started/stopped.When calling dpcm framework
api's it should acquire dpcm mutex.
This change replaces the card mutex with dpcm mutex when
dpcm apis are called.

CRs-fixed: 596103
Change-Id: I66abb823e07a0d7eb5d9687927526d785959410f
Signed-off-by: Gopikrishnaiah Anandan <agopik@codeaurora.org>