hal: Fix alignement of of buffer sent to DSP

Currently, ALIGN macro can align properly only if the buffer size
is a power of 2.
To have same PCM samples for all channels, the buffer size requires to
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.
Alignment of 96 satsfies both of the above requirements.

Change-Id: I55d261092925ee1fc57df6954ff40ac4f77494db