drm/msm/mdp4: get rid of mdp4_crtc.id

There is no reason to store CRTC id, it's a part of the drm_crtc. Drop
this member and use drm_crtc.name for the warning message.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/662576/


Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>