rockchip: rk3288-firefly: Migrate to OF_UPSTREAM

The device tree for Firefly-RK3288 in dts/upstream can be used as-is by
U-Boot, migrate board to use OF_UPSTREAM.

Add chosen stdout-path prop to board u-boot.dtsi as it is missing in DT
from dts/upstream. Also change to use the upstream power_led symbol.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3288-firefly-u-boot.dtsi b/arch/arm/dts/rk3288-firefly-u-boot.dtsi
index f953f68..13f5be2 100644
--- a/arch/arm/dts/rk3288-firefly-u-boot.dtsi
+++ b/arch/arm/dts/rk3288-firefly-u-boot.dtsi
@@ -6,10 +6,8 @@
 #include "rk3288-u-boot.dtsi"
 
 / {
-	leds {
-		power {
-			default-state = "on";
-		};
+	chosen {
+		stdout-path = "serial2:115200n8";
 	};
 };
 
@@ -73,6 +71,10 @@
 	bootph-some-ram;
 };
 
+&power_led {
+	default-state = "on";
+};
+
 &sdmmc {
 	bootph-pre-ram;
 	bootph-some-ram;