msm: vidc : Handle power collapse properly in venus HFI

When video driver gets PC_PREP_DONE from firmware, callback
response_type is not updated causing power collpase to timeout.
This change fixes the watchdog timeout issue.

Change-Id: Ibc390418747f07876b45c38c095b52ea92d5796f
Signed-off-by: Sowmya Pandiri <spandiri@codeaurora.org>