msm: vidc: schedule fw unload regardless of inst count

Remove the list_empty check for core's instance list
while deciding to schedule firmware unload. Let fw
unload work check for list_empty on core's instance
list.

Change-Id: If9b1501b95845e331cf0ade358901d788a79b19b
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>