soc: rockchip: grf: Add select correct PWM implementation on RK3368

soc: rockchip: grf: Add select correct PWM implementation on RK3368

Similar to the RK3288, the RK3368 has two different implementations of
the PWM block inside the SoC - the newer ones that we have a driver for
and that is used on every SoC and a previous variant that was likely
left as a fallback if the new one creates problems.

The devicetree is already set up for the new variant, so make sure
we actually use it - similar to the RK3288.

Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Link: https://patch.msgid.link/20251021074254.87065-4-heiko@sntech.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>