msm: camera: Modify shutdown sequence in KMD

This change ensures subdevices close before the video device
cleans up. Memory manager is currently associated with request
manager, with this change we ensure all subdevices cleanup prior
to cleaning up the request/memory manager.

Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>
Change-Id: Ia6b715025ee940ad14e4b4bbe8ed747d895fb342