msm: camera: jpeg: Fix flush with request id

This change fixes page fault because of wrong type casting.
This happens when flush is called with a request id.
Also add code to stop processing request.

Change-Id: I6d9aa9c3d71f5f83242d2ee8580bfe8380cfe36d
Signed-off-by: Suraj Dongre <sdongre@codeaurora.org>