MAINTAINERS: fix a renamed DT reference

Fix this rename:

	Documentation/devicetree/bindings/i2c/{i2c-mv64xxx.txt -> marvell,mv64xxx-i2c.yaml}

Fixes: f8bbde72

 ("dt-bindings: i2c: mv64xxx: Add YAML schemas")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>