msm: camera: remove command ack queue entry from the list.

This change makes sure that the command ack queue is properly
removed from the session's list of command ack queues. This ensures
that there aren't any outdated queues in the list.

Change-Id: I54424a8189fb2477be540cecd8277a6d4df58aa0
Signed-off-by: Ankit Premrajka <ankitp@codeaurora.org>