MAINTAINERS: dt: update display/allwinner file entry

Changeset f5a98bfe ("dt-bindings: display: Convert Allwinner display pipeline to schemas")
split Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
into several files. Yet, it kept the old place at MAINTAINERS.

Update it to point to the new place.

Fixes: f5a98bfe ("dt-bindings: display: Convert Allwinner display pipeline to schemas")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

MAINTAINERS

@@ -5552,7 +5552,7 @@ M:	Chen-Yu Tsai <wens@csie.org>
 L:	dri-devel@lists.freedesktop.org
 S:	Supported
 T:	git git://anongit.freedesktop.org/drm/drm-misc
-F:	Documentation/devicetree/bindings/display/sunxi/sun4i-drm.txt
+F:	Documentation/devicetree/bindings/display/allwinner*
 F:	drivers/gpu/drm/sun4i/
 DRM DRIVERS FOR AMLOGIC SOCS