dt-bindings:iio:adc: update motorola,cpcap-adc.yaml reference

Changeset 1ca9d1b ("dt-bindings:iio:adc:motorola,cpcap-adc yaml conversion")
renamed: Documentation/devicetree/bindings/iio/adc/cpcap-adc.txt
to: Documentation/devicetree/bindings/iio/adc/motorola,cpcap-adc.yaml.

Update its cross-reference accordingly.

Fixes: 1ca9d1b ("dt-bindings:iio:adc:motorola,cpcap-adc yaml conversion")
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/3e205e5fa701e4bc15d39d6ac1f57717df2bb4c6.1617972339.git.mchehab+huawei@kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/mfd/motorola-cpcap.txt

@@ -23,7 +23,7 @@ which are described in the following files:
 - Documentation/devicetree/bindings/input/cpcap-pwrbutton.txt
 - Documentation/devicetree/bindings/rtc/cpcap-rtc.txt
 - Documentation/devicetree/bindings/leds/leds-cpcap.txt
-- Documentation/devicetree/bindings/iio/adc/cpcap-adc.txt
+- Documentation/devicetree/bindings/iio/adc/motorola,cpcap-adc.yaml
 
 The only exception is the audio codec. Instead of a compatible value its
 node must be named "audio-codec".