pwm: rockchip: Use pwm_apply() instead of pwm_enable()

Drop the custom hook of pwm_enable() and implement pwm_apply_v1() and
pwm_apply_v2() instead.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>