msm: vidc: Fix a bug in closing the instance

When sending the SESSION END command to FW, driver
is moving to OPEN state due to a bug. This is causing
state transitions to go out of order. When session end
is recieved from FW, driver is accessing the memory which
is freed.This may cause pointer mismatch resulting random
crashes. This change fix the same.

Change-Id: I89373ccbcf72983e82119b9247ff29defc6f5305
CRs-Fixed: 468218
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>