msm: mdss: hdmi: use hardware hot plug trigger

On receiving hot plug power off event, switch off 5V
regulator in case cable is still connected to sink to
receive disconnect hardware interrupt. Do not issue
software based disconnect event in this case as it can
cause different modules to go out of sync resulting in
unstable system.

Change-Id: I19d82b62e8ad507458abd21a8a71fbcae8adefec
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>