[S390] Fix build errors (fallout from system.h disintegration)

Signed-off-by: Heiko Carstens <h.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/mmu.h b/arch/s390/include/asm/mmu.h
index 1c7d6ce..6340178 100644
--- a/arch/s390/include/asm/mmu.h
+++ b/arch/s390/include/asm/mmu.h
@@ -1,6 +1,8 @@
 #ifndef __MMU_H
 #define __MMU_H
 
+#include <linux/errno.h>
+
 typedef struct {
 	atomic_t attach_count;
 	unsigned int flush_mm;