dt-bindings: iio: rockchip: Fix 'oneOf' condition failed warning

dt-bindings: iio: rockchip: Fix 'oneOf' condition failed warning

rk3588-saradc isn't compatible with the rk3399-saradc variant,
hence, fix the following dtbs_check warning for 'oneOf' condition
failure.

DTC_CHK arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dtb
/home/shreeya/linux/arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dtb:
	saradc@fec10000: compatible: 'oneOf' conditional failed,
	one must be fixed:
	['rockchip,rk3588-saradc'] is too short
	'rockchip,saradc' was expected
	'rockchip,rk3066-tsadc' was expected
	'rockchip,rk3399-saradc' was expected

Fixes: 2daf2ae9793d ("dt-bindings: iio: adc: Add rockchip,rk3588-saradc string")
Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230610143601.173307-1-shreeya.patel@collabora.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>