msm: vidc: Initialize the completion before sending the command

For ABORT command driver is sending the command to Venus first and
then initializing the completion. So by the time driver initializes
venus might send the response back. So this response may get lost
and driver eventually times out. Hence initialize the completion
before sending the command.

Change-Id: Ib8a4f76f1bf34f39f305ab49affca95007f9d57d
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>