MAINTAINERS: update ti,dac7612.yaml reference

Changeset 8b74e06b ("dt-bindings:iio:dac:ti,dac7612 yaml conversion")
renamed: Documentation/devicetree/bindings/iio/dac/ti,dac7612.txt
to: Documentation/devicetree/bindings/iio/dac/ti,dac7612.yaml.

Update its cross-reference accordingly.

Fixes: 8b74e06b ("dt-bindings:iio:dac:ti,dac7612 yaml conversion")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/04039b6991838f0107a42ccb0d9774cb8873a61a.1617279355.git.mchehab+huawei@kernel.org


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>