[S390] Get rid of a lot of sparse warnings.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c
index 607f50e..fb87e23 100644
--- a/arch/s390/mm/cmm.c
+++ b/arch/s390/mm/cmm.c
@@ -414,7 +414,7 @@
 }
 #endif
 
-struct ctl_table_header *cmm_sysctl_header;
+static struct ctl_table_header *cmm_sysctl_header;
 
 static int
 cmm_init (void)