msm: camera: Cleanup msm generic buf queue handling

Clean-up the msm camera generic buff queue when all
client closes the handle and also provide init-deinit
ioctl for cpp to open-close the buff mngr handle.

Change-Id: Ie484174e0ffaee02e85c9c9cda8ac26103aaddd0
CRs-Fixed: 582261
Signed-off-by: Hariram Purushothaman <hpurus@codeaurora.org>