msm: camera: Handle request to flush stream buffers

When client requests to flush stream buffers, ensure to queue
all the buffers mapped on that stream back to the client.

Change-Id: I8014701e7fb7e5c14003e9521f5540bfaa5a3e54
Signed-off-by: Azam Sadiq Pasha Kapatrala Syed <akapatra@codeaurora.org>
Signed-off-by: Hariram Purushothaman <hariramp@codeaurora.org>