msm: camera: Cleanup msm_generic_buff list while close

Cleanup the camera msm generic buffer manager list
when all camera v4l2 nodes are closed to avoid any
staggered buff list which might used in the next
session. Which leads to crash due to invalid pointer
access.

Change-Id: I27636533621d3329bcc5dffba8c003d2cdc252c2
CRs-Fixed: 599983
Signed-off-by: Azam Sadiq Pasha Kapatrala Syed <akapatra@codeaurora.org>