[S390] sparse: fix sparse static warnings

Make functions and data static to avoid sparse warnings.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 1d05d66..64b761a 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -635,7 +635,7 @@
 	asm volatile(".word 0x0002");
 }
 
-void __kprobes jprobe_return_end(void)
+static void __used __kprobes jprobe_return_end(void)
 {
 	asm volatile("bcr 0,0");
 }