ARM: dts: mvebu: armada-390: add missing compatibility string and bracket

The armada-390.dtsi was broken since the first patch which adds Device Tree
files for Armada 39x SoC was introduced.
Signed-off-by: NGrzegorz Jaszczyk <jaz@semihalf.com>
Acked-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Cc: <stable@vger.kernel.org> # 4.0+
Fixes 538da83d ("ARM: mvebu: add Device Tree files for Armada 39x SoC and board")
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm/boot/dts/armada-390.dtsi

@@ -47,6 +47,8 @@
 #include "armada-39x.dtsi"
 
 / {
+	compatible = "marvell,armada390";
+
 	soc {
 		internal-regs {
 			pinctrl@18000 {
@@ -54,4 +56,5 @@
 				reg = <0x18000 0x20>;
 			};
 		};
+	};
 };