dt-bindings: pwm: rockchip: Add rockchip,rk3528-pwm

Document pwm compatible for rk3528 which is fallback compatible
of rk3328-pwm group.

Signed-off-by: Chukun Pan <amadeus@jmu.edu.cn>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Uwe Kleine-König <ukleinek@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20250307120004.959980-2-amadeus@jmu.edu.cn


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>