s390: make couple of functions and variables static

As reported by sparse these can and should be static.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/mm/mmap.c

@@ -32,7 +32,7 @@
 #include <asm/pgalloc.h>
 
 unsigned long mmap_rnd_mask;
-unsigned long mmap_align_mask;
+static unsigned long mmap_align_mask;
 
 static unsigned long stack_maxrandom_size(void)
 {