msm: vidc: Rectify core lock and core state sequence

When core fails to initialize, venus firmware is
unloaded. Move the core state to uninit (unloaded)
state. Mutex lock/unlock sequence is corrected.

Change-Id: I4a71d53db038e1533cf7cc799f3d28a4c5c89619
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>