msm: mdss: prevent slow path error during DSI underflow recovery

When DSI underflow is reported, ctl reset is preformed which requires
certain critical regions to be protected by mutex. However this reset
itself doesn't need to be protected by koff_lock spinlock and thus move
it out of spinlock to prevent mutex locking while holding spinlocks.

Change-Id: I9a5da66c3db5c3839fa45a25898a5d610134594e
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>