s390/vdso: fix access-list entry initialization

The access-list entry is supposed to have the fetch-only bit set, however
a reserved bit got set instead.
Userspace isn't able to write to the page anyway since the accessed page
has the read-only bit set. So this saves us only for bad surprises in the
future if the reserved bit gets used.
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/vdso.c

@@ -125,7 +125,7 @@ int vdso_alloc_per_cpu(struct _lowcore *lowcore)
 		psal[i] = 0x80000000;
 
 	lowcore->paste[4] = (u32)(addr_t) psal;
-	psal[0] = 0x20000000;
+	psal[0] = 0x02000000;
 	psal[2] = (u32)(addr_t) aste;
 	*(unsigned long *) (aste + 2) = segment_table +
 		_ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;