GFS2: Add initialization for address space in super block

Spotted by Andy Price. This should fix the odd messages from
lockdep caused by 70d4ee94b370c5ef54d0870600f16bd92d18013c

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Price <anprice@redhat.com>
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index 94aab31..3b820b6 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -102,6 +102,7 @@
 
 	mapping = &sdp->sd_aspace;
 
+	address_space_init_once(mapping);
 	mapping->a_ops = &gfs2_meta_aops;
 	mapping->host = sb->s_bdev->bd_inode;
 	mapping->flags = 0;