drm/msm/mdp4: Consistently use the "mdp4_" namespace

drm/msm/mdp4: Consistently use the "mdp4_" namespace

Functions and other stuff all start with "mdp4_", except a few ones that
start with "mpd4_" (d and p switched)

Make things consistent and use "mdp4_" everywhere.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/661306/
Link: https://lore.kernel.org/r/6b9076268548c52ec371e9ed35fee0dd8fcb46ef.1751044672.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>