sysctl: Use header file for sysctl knob declarations on sparc.

This also takes care of a sparse warning as scons_pwroff's definition
point.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/arch/sparc64/kernel/reboot.c b/arch/sparc64/kernel/reboot.c
index 11f2496..ef89d3d 100644
--- a/arch/sparc64/kernel/reboot.c
+++ b/arch/sparc64/kernel/reboot.c
@@ -7,6 +7,7 @@
 #include <linux/module.h>
 #include <linux/pm.h>
 
+#include <asm/system.h>
 #include <asm/oplib.h>
 #include <asm/prom.h>