config: evb-rk3399: enable PWM_ROCKCHIP

PWM_ROCKCHIP need to enable for PWM regulator, this config
is missing during rebase and new patch set in previous submission.
Signed-off-by: NKever Yang <kever.yang@rock-chips.com>
Acked-by: NSimon Glass <sjg@chromium.org>

configs/evb-rk3399_defconfig

@@ -24,6 +24,7 @@ CONFIG_ROCKCHIP_DWMMC=y
 CONFIG_ROCKCHIP_SDHCI=y
 CONFIG_PINCTRL=y
 CONFIG_ROCKCHIP_RK3399_PINCTRL=y
+CONFIG_PWM_ROCKCHIP=y
 CONFIG_REGULATOR_PWM=y
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_RAM=y