arm64: dts: amlogic: meson-g12b-radxa-zero2: fix pwm clock names

Fixes the following bindings check error:
 - pwm@2000: clock-names: 'oneOf' conditional failed, one must be fixed:
	['clkin4'] is too short
	'clkin4' is not one of ['clkin0', 'clkin1']
	'clkin0' was expected
 - pwm@7000: clock-names: 'oneOf' conditional failed, one must be fixed:
	['clkin3'] is too short
	'clkin3' is not one of ['clkin0', 'clkin1']
	'clkin0' was expected
 - pwm@19000: clock-names: 'oneOf' conditional failed, one must be fixed:
	['clkin2'] is too short
	'clkin2' is not one of ['clkin0', 'clkin1']
	'clkin0' was expected

Fixes: d747e7f7 ("arm64: dts: meson: add support for Radxa Zero2")
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20230207-b4-amlogic-bindings-fixups-v2-v1-4-93b7e50286e7@linaro.org


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>