msm: mdss: add MDP hw revision check for msm8939 panic/robust feature

Add MDP hw revision check to support panic/robust signalling
feature for msm8939. This feature enables MDP hardware to send
panic/robust signal to bimc based on fill level for all pipes
connected to realtime interfaces.

Change-Id: Idf8908eb6e4d2827d02f929161e43b58ca56757a
Signed-off-by: Radhika Ranjan Soni <rrsoni@codeaurora.org>