drm/msm/dpu: don't clear IRQ register twice

We already clear the IRQ status register before processing IRQs, so do
not clear the register again. Especially do not clear the IRQ status
_after_ processing the IRQ as this way we can loose the event.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Link: https://lore.kernel.org/r/20210617222029.463045-3-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>