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>

MAINTAINERS

@@ -17694,7 +17694,7 @@ TEXAS INSTRUMENTS' DAC7612 DAC DRIVER
 M:	Ricardo Ribalda <ribalda@kernel.org>
 L:	linux-iio@vger.kernel.org
 S:	Supported
-F:	Documentation/devicetree/bindings/iio/dac/ti,dac7612.txt
+F:	Documentation/devicetree/bindings/iio/dac/ti,dac7612.yaml
 F:	drivers/iio/dac/ti-dac7612.c
 
 TEXAS INSTRUMENTS DMA DRIVERS