msm: mdss: make the mdss debugfs implementation generic

Remove the core specific details in the debugfs implementation via
a defined debug interface.

Change-Id: I2bf9ac47e0121f1f269d8d82274143d760305526
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>
msm: mdss: disable MDP hw underflow recovery

When MDP underflows, hardware will automatically try to issue a reset to
recover from it. Potential issue has been identified when reset happens
on two video interfaces at the same time which may lead to a hw lockup.
To avoid such situations disable the hardware underflow recovery, MDP
will still automatically recover at the beginning of next frame.

Change-Id: I3473486e229e67f6213db83a0ecb34333a977d4f
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>