msm: mdss: hdmi: clear interrupt in order to prevent interrupt storm

With the new approach of separating isr and enabling interrupt, it
is mandatory for panel drivers to at least clear the interrupt if
is received unexpectedly. This patch makes such a change for interrupts
within HDMI domain.

Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>
Change-Id: I532b3cc9c1643536218a51494c0212e0839a5f20