arm: mvebu: fix compatible string in armada-370-xp.dtsi

All the Device Tree files for Armada 370 and XP SoCs and boards use
the "armada-370-xp" common compatible string, except
armada-370-xp.dtsi which was specifying "armada_370_xp".

Fix this inconsistency by making armada-370-xp.dtsi declare a
compatible string of "armada-370-xp" like everyone else.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm/boot/dts/armada-370-xp.dtsi

@@ -20,7 +20,7 @@
 
 / {
 	model = "Marvell Armada 370 and XP SoC";
-	compatible = "marvell,armada_370_xp";
+	compatible = "marvell,armada-370-xp";
 
 	cpus {
 		cpu@0 {