drm/msm/mdp4: refactor HW revision detection into read_mdp_hw_revision

Inspired by MDP5 code.
Also use DRM_DEV_INFO for MDP version as MDP5 does.

Cosmetic change: uint32_t -> u32 - checkpatch suggestion.

Signed-off-by: David Heidelberg <david@ixit.cz>
Link: https://lore.kernel.org/r/20210705231641.315804-1-david@ixit.cz


Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>