ARM: DTS: Resync am3517-evm.dts with Linux 5.0-rc3

The chosen node was added in the kernel.  This may come in handy
in the future, so resync with 5.0-rc3

Signed-off-by: Adam Ford <aford173@gmail.com>

arch/arm/dts/am3517-evm.dts

@@ -20,6 +20,10 @@
 		display0 = &lcd0;
 	};
 
+	chosen {
+		stdout-path = &uart3;
+	};
+
 	memory@80000000 {
 		device_type = "memory";
 		reg = <0x80000000 0x10000000>; /* 256 MB */