drm/msm/dpu: Further cleanups for static inline functions

Remove more static inline functions that are lightly used and/or
very simple and easy to build into the calling functions.

v3: Fix a nit from Sean Paul
v2: Removed another unused function from dpu_hw_lm.c and add back
dpu_crtc_get_client_type() since there was a question regarding
its usefulness.

Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>