msm: vidc: Free VMEM if core goes in to bad state

If the Venus core goes in to bad state, the video driver
was skipping unset and free of VMEM before firmware was
unloaded. This would cause VMEM to be not set for the
next session, as __alloc_set_imem() would bail out
complaining that VMEM is already allocated. Not setting
VMEM could cause the video session to fail.

Change-Id: I76539bfb34ae50dd07566e50f377d98d51ed6e6f
Signed-off-by: Arun Menon <avmenon@codeaurora.org>