MAINTAINERS: update gemini.yaml reference

Changeset 7da6ebf5 ("dt-bindings: arm: Convert Gemini boards to YAML")
renamed: Documentation/devicetree/bindings/arm/gemini.txt
to: Documentation/devicetree/bindings/arm/gemini.yaml.

Update its cross-reference accordingly.

Fixes: 7da6ebf5 ("dt-bindings: arm: Convert Gemini boards to YAML")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/dd52c97597a073a5830ecf115d4a6516eebc6d6a.1634630486.git.mchehab+huawei@kernel.org

MAINTAINERS

@@ -1873,7 +1873,7 @@ M:	Linus Walleij <linus.walleij@linaro.org>
 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.txt
+F:	Documentation/devicetree/bindings/arm/gemini.yaml
 F:	Documentation/devicetree/bindings/net/cortina,gemini-ethernet.txt
 F:	Documentation/devicetree/bindings/pinctrl/cortina,gemini-pinctrl.txt
 F:	Documentation/devicetree/bindings/rtc/faraday,ftrtc010.yaml