MAINTAINERS: update adi,ad5758.yaml reference

Changeset 1e6536ee ("dt-bindings:iio:dac:adi,ad5758 yaml conversion")
renamed: Documentation/devicetree/bindings/iio/dac/ad5758.txt
to: Documentation/devicetree/bindings/iio/dac/adi,ad5758.yaml.

Update its cross-reference accordingly.

Fixes: 1e6536ee ("dt-bindings:iio:dac:adi,ad5758 yaml conversion")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

MAINTAINERS

@@ -1142,7 +1142,7 @@ W:	http://ez.analog.com/community/linux-device-drivers
 F:	Documentation/ABI/testing/sysfs-bus-iio-frequency-ad9523
 F:	Documentation/ABI/testing/sysfs-bus-iio-frequency-adf4350
 F:	Documentation/devicetree/bindings/iio/*/adi,*
-F:	Documentation/devicetree/bindings/iio/dac/ad5758.txt
+F:	Documentation/devicetree/bindings/iio/dac/adi,ad5758.yaml
 F:	drivers/iio/*/ad*
 F:	drivers/iio/adc/ltc249*
 F:	drivers/iio/amplifiers/hmc425a.c