hal: bug fixes for PCM offload

When pcm offload is done, override the buffer size
that was calculated and use the value from the system property
Make write call blocking if small buffers are used in offload
Update latency value for pcm offload with small buffer hint based
on period size and period count.

Change-Id: Ic74caa6bd172c8e4554384e9fa98a5137117f07c