MAINTAINERS: update cortina,gemini-ethernet.yaml reference

Changeset 208b65f ("dt-bindings: net: convert net/cortina,gemini-ethernet to yaml")
renamed: Documentation/devicetree/bindings/net/cortina,gemini-ethernet.txt
to: Documentation/devicetree/bindings/net/cortina,gemini-ethernet.yaml.

Update its cross-reference accordingly.

Fixes: 208b65f ("dt-bindings: net: convert net/cortina,gemini-ethernet to yaml")
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/d27b5d508fb757147b720bf573ce5a2e3fc5920e.1654529011.git.mchehab@kernel.org

Author: mchehab

MAINTAINERS

@@ -2009,7 +2009,7 @@ L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
 T:	git git://github.com/ulli-kroll/linux.git
 F:	Documentation/devicetree/bindings/arm/gemini.yaml
-F:	Documentation/devicetree/bindings/net/cortina,gemini-ethernet.txt
+F:	Documentation/devicetree/bindings/net/cortina,gemini-ethernet.yaml
 F:	Documentation/devicetree/bindings/pinctrl/cortina,gemini-pinctrl.txt
 F:	Documentation/devicetree/bindings/rtc/faraday,ftrtc010.yaml
 F:	arch/arm/boot/dts/gemini*