rockchip: dts: evb-rk3399: add gmac support

Enable gmac for evb-rk3399.

Change-Id: I85e35667e08e22e38577e63eb0e65731fc9c69b6
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/include/dt-bindings/pinctrl/rockchip.h b/include/dt-bindings/pinctrl/rockchip.h
index ecb76c7..7d454a2 100644
--- a/include/dt-bindings/pinctrl/rockchip.h
+++ b/include/dt-bindings/pinctrl/rockchip.h
@@ -17,6 +17,8 @@
 #define RK_GPIO4	4
 #define RK_GPIO6	6
 
+#define RK_PB7		15
+
 #define RK_FUNC_GPIO	0
 #define RK_FUNC_1	1
 #define RK_FUNC_2	2