drm/msm: dpu: Remove 'inline' from several functions

Per chapter 15 of coding-style, removing 'inline' keyword from functions
that are larger than a typical macro. In a couple of cases I've
simplified the function and kept the inline.

Reviewed-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>