hal: Fix alignement of buffer sent to DSP for multichannel clips

 - currently buffer size is Aligned with 96 which is not multiple
   of some channels(5,7).
 - Buffer size must be multiple of (number of channels * bytes per sample).
   For writes to succeed, the buffer must be written at address which is
   multiple of 32.
 - Alignments of (number of channels * bytes per sample)*32 satisfies both
   of the above requirements.

Change-Id: I20de875615141a4a331383a5348abd28b97306f7