msm-pcm-q6: Add support for flexible recording period size

- Current implementation supports only fixed buffer size
  of 320 bytes only for audio recording. This results in
  performance overhead for recording at higher sample rate.
- Added support for flexible period size so that user can
  use larger buffers for recording at higher sample rates.

Signed-off-by: SathishKumar Mani<smani@codeaurora.org>
Signed-off-by: Iliyan Malchev <malchev@google.com>

Conflicts:
	sound/soc/msm/msm-pcm-q6.c

Change-Id: Id767a5286a0464608f792b64a788f9cfb7c6ea08