msm: camera: icp: release mutex properly in flush function

Mutex lock was not released when there is nothing to be flushed
in ICP driver and recovery is not enabled, which will cause
issue when release HW tries to acquire same mutex. This change
properly release the mutex lock in such scenario.

Change-Id: I86804b529694e64fdea1550ac36834c2c356cdd4
Signed-off-by: Junzhe Zou <jnzhezou@codeaurora.org>