[GFS2] Tidy gfs2_unstuffer_page

Tidy up gfs2_unstuffer_page by:

 a) Moving it into bmap.c
 b) Making it static
 c) Calling it directly from gfs2_unstuff_dinode
 d) Updating all callers of gfs2_unstuff_dinode due to one less
    required argument.

It doesn't change the behaviour at all.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index f62223b..563b99e 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -173,7 +173,7 @@
 		return -EINVAL;
 
 	if (gfs2_is_stuffed(ip)) {
-		error = gfs2_unstuff_dinode(ip, NULL, NULL);
+		error = gfs2_unstuff_dinode(ip, NULL);
 		if (error)
 			return error;
 	}