rockchip: rk3368: add Sheep board

Sheep board is designed by Rockchip as a EVB for rk3368.
Currently it is able to boot a linux kernel and system
to console with the miniloader run as fist level loader.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index aceb29e..7655d4d 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -41,6 +41,7 @@
 	rk3288-veyron-mickey.dtb \
 	rk3288-veyron-minnie.dtb \
 	rk3328-evb.dtb \
+	rk3368-sheep.dtb \
 	rk3399-evb.dtb \
 	rk3399-firefly.dtb \
 	rk3399-puma.dtb