dt-bindings: fix up for vendor prefixes file conversion

Link: Link: http://patchwork.freedesktop.org/patch/msgid/20190521105151.51ffa942@canb.auug.org.au


Fixes: 374ed542 ("Merge drm/drm-next into drm-misc-next")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>