drm/msm/dpu: squash dpu_core_irq into dpu_hw_interrupts

With dpu_core_irq being the wrapper around dpu_hw_interrupts, there is
little sense in having them separate. Squash them together to remove
another layer of abstraction (hw_intr ops).

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Link: https://lore.kernel.org/r/20210617222029.463045-2-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>