msm: vidc: Do not enable power if close is called during SYS_ERROR handling

If msm_vidc_close() is called while sys error handling is in progress
and before firmware gets loaded, then power_on() will be called in
venus HFI. As the instance and core are still in invalid state,
we end up calling __unvote_buses() that accesses NULL device pointer
causing kernel panic. This change will address the race condition.

Change-Id: If3d815c12f425bd7b4262a43f1c9741f46a8b62f
CRs-Fixed: 857826
Signed-off-by: Sowmya Pandiri <spandiri@codeaurora.org>