msm: vidc: Remove unncessary unmap function calls

Calling unncessary unmap function resulting in
target reset. This change resolves the issue by
removing unncessary unmap functions in video driver.

Change-Id: I0b501f0a7115bba085b067a5e78172df210da8f1
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>
Signed-off-by: Sridhar Gujje <sgujje@codeaurora.org>