s390/mm: provide PAGE_SHARED define

Only needed to make some drivers compile...

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
index 098adbb..a009d4d 100644
--- a/arch/s390/include/asm/pgtable.h
+++ b/arch/s390/include/asm/pgtable.h
@@ -385,6 +385,7 @@
 #define PAGE_RW		__pgprot(_PAGE_TYPE_RW)
 
 #define PAGE_KERNEL	PAGE_RW
+#define PAGE_SHARED	PAGE_KERNEL
 #define PAGE_COPY	PAGE_RO
 
 /*