drm/msm/sde: disable irq on startup to match power event

Update irq post install to disable irq to match
power event startup state. Irq is currently enabled
after registration. However, power event assumes irq
to be disabled by default and generates unbalanced enable
warning on first power on event.

Change-Id: I3e9166782797ad286cf4112d55c458c3a85f68d1
Signed-off-by: Alan Kwong <akwong@codeaurora.org>