drm/modes: Kill off the oddball DRM_MODE_TYPE_CRTC_C vs. DRM_MODE_TYPE_BUILTIN handling

For some reason drm_mode_set_crtcinfo() does nothing if the mode has
the DRM_MODE_TYPE_BUILTIN flag set without the other bit from
DRM_MODE_TYPE_CRTC_C also set. I have zero idea what that is supposed
to achieve, but since we have no users for neither flag bit let's kill
this nonsense off.

v2: Fix typo in commit message

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171114183258.16976-7-ville.syrjala@linux.intel.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>