sh: nommu fault handler needs signal.h.

Trivial build fix.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/mm/fault-nommu.c

@@ -12,6 +12,7 @@
 #include <linux/mm.h>
 #include <linux/hardirq.h>
 #include <linux/kprobes.h>
+#include <linux/signal.h>
 #include <asm/system.h>
 #include <asm/ptrace.h>
 #include <asm/kgdb.h>