make do_sigaltstack() static

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/kernel/signal.c b/kernel/signal.c
index 87c09e3..6919050 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3129,7 +3129,7 @@
 	return 0;
 }
 
-int 
+static int 
 do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
 {
 	stack_t oss;