dt-bindings: iio: adc: renesas,rcar-gyroadc: Fix adi,ad7476 compatible value

dt-bindings: iio: adc: renesas,rcar-gyroadc: Fix adi,ad7476 compatible value

The conversion to json-schema accidentally dropped the "ad" part prefix
from the compatible value.

Fixes: 8c41245872e2 ("dt-bindings:iio:adc:renesas,rcar-gyroadc: txt to yaml conversion.")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/6b328a3f52657c20759f3a5bb2fe033d47644ba8.1683635404.git.geert+renesas@glider.be
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>