ALSA: compress: Add snd_compress_free()

We are not currently freeing the compressed devices at module
unload time. This could be used to help, but more investigation
needs to be done to resolve this issue.

This patch is WIP

Change-Id: I6cf8bcc56e4d446d83e9a0e63b79db3da378a901
Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Git-commit: b2ebfd20ecb255b8e575ea8b6fad8d1affc2ea77
Git-repo: https://android.googlesource.com/kernel/msm


Signed-off-by: Dhananjay Kumar <dhakumar@codeaurora.org>
[bgoswami@codeaurora.org: resolved merge conflicts]
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Meng Wang <mwang@codeaurora.org>