ASoC: msm: handle partial writes in compress driver

Compress driver might have to deal with arbitrary sized writes
in the middle of playback. To deal with it, accumulate fragment_size worth
data before sending to the DSP. Use the drain trigger to push any
pending buffer to the DSP.

Change-Id: I8d95a9945076142f16adb99a295f6a9e84039cbb
Signed-off-by: Haynes Mathew George <hgeorge@codeaurora.org>
Signed-off-by: Eric Laurent <elaurent@google.com>
Git-commit: 6ac9bb553c1285266b2ac28800abec240cd76e17
Git-repo: https://android.googlesource.com/kernel/msm


[dhakumar@codeaurora.org: resolved merge conflicts]
Signed-off-by: Dhananjay Kumar <dhakumar@codeaurora.org>