disp: msm: sde: move vm-ownership check to crtc custom events

Currently all the custom event register/unregister calls are
blocked based on the vm-ownership checks. Avoid this check
for connector events as it has only software updates unlike
the crtc events which directly touch the HW registers. This
allows the connector events to be registered before the first
commit where the VM ownership is obtained.

Change-Id: Id78e365929cb958ead10221b9267f1c1c0406a27
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>