arm64: dts: rockchip: fix supplies for pwm regulators

The supply-name for pwm-regualators is "pwm", so the property
needs to be pwm-supply, not vin-supply as in a number of boards.

In all cases changed here, the supplying regulator is always
an always-on fixed-regulator, so there will be no functional
change and only a change in the regulator hirarchy, as can be seen
for example in the regulator-summary.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20211227234529.1970281-2-heiko@sntech.de