rockchip: pwm: add mask for config setting

Use mask to clear old setting before direct set the new config,
or else there it will mess up the config when it's not the same
with default value.

Fixes: 3851059 rockchip: Setup default PWM flags
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

arch/arm/include/asm/arch-rockchip/pwm.h

@@ -25,9 +25,11 @@ check_member(rk3288_pwm, ctrl, 0xc);
 
 #define PWM_DUTY_POSTIVE                (1 << 3)
 #define PWM_DUTY_NEGATIVE               (0 << 3)
+#define PWM_DUTY_MASK			(1 << 3)
 
 #define PWM_INACTIVE_POSTIVE            (1 << 4)
 #define PWM_INACTIVE_NEGATIVE           (0 << 4)
+#define PWM_INACTIVE_MASK		(1 << 4)
 
 #define PWM_OUTPUT_LEFT                 (0 << 5)
 #define PWM_OUTPUT_CENTER               (1 << 5)

drivers/pwm/rk_pwm.c

@@ -29,6 +29,7 @@ static int rk_pwm_set_invert(struct udevice *dev, uint channel, bool polarity)
 	struct rk_pwm_priv *priv = dev_get_priv(dev);
 
 	debug("%s: polarity=%u\n", __func__, polarity);
+	priv->enable_conf &= ~(PWM_DUTY_MASK | PWM_INACTIVE_MASK);
 	if (polarity)
 		priv->enable_conf |= PWM_DUTY_NEGATIVE | PWM_INACTIVE_POSTIVE;
 	else