Misc. cleanups

[Jesse Barnes]

Just some cleanups for unused fields in drm_crtc.h and some comment
corrections.  I also removed a few DRM_ERRORs from drm_crtc.c (things
actually weren't as bad as I feared).

Next step is to remove a whole slew of DRM_DEBUG calls unless people are
really attached to them.  I find them to just get in the way when I'm
debugging a display problem, so I convert the ones I care about to
DRM_ERROR temporarily and add several of my own...

Thanks,
Jesse