drm/msm/dpu: stop using raw IRQ indices in the kernel output

In preparation to reworking IRQ indcies, stop using raw IRQ indices in
kernel output (both printk and debugfs). Instead use a pair of register
index and bit. This corresponds closer to the values in HW catalog.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/550933/
Link: https://lore.kernel.org/r/20230802100426.4184892-7-dmitry.baryshkov@linaro.org