drm: Remove unnecessary junk from drm_crtc.h

drm_crtc.h is including several entirely unnecessary headers,
and also contains unused forward declarations. Remove it all.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220613200317.11305-6-ville.syrjala@linux.intel.com


Acked-by: Jani Nikula <jani.nikula@intel.com>