rockchip: pinctrl: rk3399: Add support for UART3.

This patch adds the missing GRF bit definitions for UART3 on the RK3399.

Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/include/asm/arch-rockchip/grf_rk3399.h b/arch/arm/include/asm/arch-rockchip/grf_rk3399.h
index b32c7d5..dd89cd2 100644
--- a/arch/arm/include/asm/arch-rockchip/grf_rk3399.h
+++ b/arch/arm/include/asm/arch-rockchip/grf_rk3399.h
@@ -423,6 +423,10 @@
 	GRF_GPIO3B6_SEL_SHIFT   = 12,
 	GRF_GPIO3B6_SEL_MASK    = 3 << GRF_GPIO3B6_SEL_SHIFT,
 	GRF_MAC_RXCLK           = 1,
+	GRF_UART3_SIN           = 2,
+	GRF_GPIO3B7_SEL_SHIFT   = 14,
+	GRF_GPIO3B7_SEL_MASK    = 3 << GRF_GPIO3B7_SEL_SHIFT,
+	GRF_UART3_SOUT          = 2,
 
 	/* GRF_GPIO3C_IOMUX */
 	GRF_GPIO3C1_SEL_SHIFT	= 2,