msm: vidc: send release buffers cmd during instance clean up

During instance cleanup, if internal or output buffer
list is not empty, respective buffers are unmapped.
Modify the cleanup instance to send release buffers to
video core if internal or output buffer list is not
empty and then unmap the respective buffers.

CRs-Fixed: 619239
Change-Id: I56bd4248173992dedfb36098dfa9ddf35fc12a4e
Signed-off-by: Rajeshwar Kurapaty <rkurapat@codeaurora.org>