disp: msm: sde: fix Trusted-ui state transition check

Fix the checks done as part of the trsuted-ui transition.
Allow full validation to go through whenever the new vm request
or old vm request is not NONE. Split the checks and the vm acquire,
so vm acquire can be done after all necessary checks are over.

Change-Id: I91165010ad110193c2ca3947af8c6504cd259919
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>