MAINTAINERS: update ste,mcde.yaml reference

Changeset 2abb0b99 ("dt-bindings: display: mcde: Convert to YAML schema")
renamed: Documentation/devicetree/bindings/display/ste,mcde.txt
to: Documentation/devicetree/bindings/display/ste,mcde.yaml.

Update its cross-reference accordingly.

Fixes: 2abb0b99 ("dt-bindings: display: mcde: Convert to YAML schema")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

MAINTAINERS

@@ -5779,7 +5779,7 @@ DRM DRIVER FOR ST-ERICSSON MCDE
 M:	Linus Walleij <linus.walleij@linaro.org>
 S:	Maintained
 T:	git git://anongit.freedesktop.org/drm/drm-misc
-F:	Documentation/devicetree/bindings/display/ste,mcde.txt
+F:	Documentation/devicetree/bindings/display/ste,mcde.yaml
 F:	drivers/gpu/drm/mcde/
 
 DRM DRIVER FOR TDFX VIDEO CARDS