drm: WARN when trying to add enum value > 63 to a bitmask property

Enum values >63 with a bitmask property is a programmer error. WARN
when someone is attempting this.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180306164849.2862-3-ville.syrjala@linux.intel.com


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>