msm: mdss: clear MDP3 DMA read ptr intr if detected before clk disable

Before disabling the DMA read ptr interrupt and turning off the clks,
there is a possibility that some other CPU might have received
READ_PTR ISR few microseconds before and started to process it.
By the time the ISR reaches the register read instructions,
the clks might be disabled and cause NOC error. To avoid such cases,
check for the intr status after disabling the ISR and clear the irq
before disabling the clks.

Change-Id: Idcc412bea6711e5bb62903c546ce54ff8243eadc
Signed-off-by: Sachin Bhayare <sachin.bhayare@codeaurora.org>