msm: mdss: hdmi: Add MHL handshake

Add HPD (Hot Plug Detect) on/off and HPD line high or low pull
handshake between MHL (Mobile High-Definition Link) and HDMI
so that both the drivers are in sync on cable connect and
disconnect.

Change-Id: Ia3264983ba3b81c499e287fa6922e1511bdf65a7
Signed-off-by: Ajay Singh Parmar <aparmar@codeaurora.org>