rockchip: pwm: fix the register layout for the PWM controller

According to rk3288 spec, the pwm register order is:
    PWM_PWM0_CNT,
    PWM_PWM0_PERIOD_HPR,
    PWM_PWM0_DUTY_LPR,
    PWM_PWM0_CTRL
but the source code's order is:
  struct rk3288_pwm {
    u32 cnt;
    u32 duty_lpr;
    u32 period_hpr;
    u32 ctrl;
  };

So, correct it here. It is the same as RK3399.

Signed-off-by: Eric Gao <eric.gao@rock-chips.com>
Edited the commit message:
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>