msm: vidc: fix cvp session close issue

Video driver tries to unregister the buffers which
are not unregistered by the userspace client in
deinitialization. Unregistering the buffers is not
required as the session will be closed anyway. So
simply try session close in msm_cvp_inst_deinit()
to avoid errors due to unregistering buffers.

Change-Id: Id9ae0683498dbbc1451055bf04a7fb7513248391
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>