MAINTAINERS: update current-sense-shunt.yaml reference

Changeset ce66e52b ("dt-bindings:iio:afe:current-sense-shunt: txt to yaml conversion.")
renamed: Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
to: Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml.

Update its cross-reference accordingly.

Fixes: ce66e52b ("dt-bindings:iio:afe:current-sense-shunt: txt to yaml conversion.")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

MAINTAINERS

@@ -8712,7 +8712,7 @@ M:	Peter Rosin <peda@axentia.se>
 L:	linux-iio@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml
-F:	Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
+F:	Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml
 F:	Documentation/devicetree/bindings/iio/afe/voltage-divider.txt
 F:	drivers/iio/afe/iio-rescale.c