msm: mdss: double check dynamic fps done interrupt

There can be a scenario where the DSI hardware finished the
dynamic fps operation and updated the DSI interrupt status
bit but the isr is not triggered. This is possible under
heavy system load where the interrupts are disabled by some
other thread on the CPU where MDSS IRQ is affined. Double
check the status of dynamic fps operation by reading back
the DSI interrupt status bit once the wait for interrupt times
out.

Change-Id: Iebe5ab3f6b43b4b3e61666a600488e8ce50f6995
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>