drm: Check property/enum name length

Reject requests to add properties/enums with an overly long name.
Previously we would have just silently truncated the string and exposed
it userspace.

v2: drm_property_create() returns a pointer

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180302140300.31110-1-ville.syrjala@linux.intel.com


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