msm: mdss: fix display lk to kernel transition issue

Earlier, during lk to kernel transition, display was
shut down and turned on again.  During shutdown, the
previously allocated overlay resource was released
and the vsync was disabled.  To distinguish between
normal shutdown and lk to kernel transition case,
a separate function is added to address the transition
use case.

Change-Id: Ib30abb4a0f97a46260dfd09ad91f59035794e45e
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>