ARM: mvebu: add missing header

The definition for SIGBUS may not be visible without including
linux/signal.h, as I found during randconfig testing.

Adding an explicit include is certainly the right thing to do.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NJason Cooper <jason@lakedaemon.net>
Acked-by: NGregory Clement <gregory.clement@free-electrons.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>

arch/arm/mach-mvebu/armada-370-xp.c

@@ -21,6 +21,7 @@
 #include <linux/clocksource.h>
 #include <linux/dma-mapping.h>
 #include <linux/mbus.h>
+#include <linux/signal.h>
 #include <linux/slab.h>
 #include <asm/hardware/cache-l2x0.h>
 #include <asm/mach/arch.h>