msm: vidc: Fix register/unregister buffer done failure

Register/Unregister buffer done is not being sent to userspace
clients as the response from video firmware is ignored in driver.
Fix the same by not ignoring buffer done responses.

Change-Id: Ib640501a0d8ada999c2b27ac1f39a849874aa7f2
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>