Pimp drm_property_type_valid() to check for more fails with the
property flags. Also make the check before adding the property,
and bail out if things look bad.

Since we're now chekcing for more than the type let's also
change the function name to drm_property_flags_valid().
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180306164849.2862-6-ville.syrjala@linux.intel.comReviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>