drm/msm/dpu: merge struct dpu_irq into struct dpu_hw_intr

As dpu_core_irq was merged into dpu_hw_intr, merge data structures too,
removing the need for a separate data structure.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Link: https://lore.kernel.org/r/20210617222029.463045-4-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>