GFS2: Fix typo in stuffed file data copy handling

trunc_start() in bmap.c incorrectly uses sizeof(struct gfs2_inode) instead of
sizeof(struct gfs2_dinode).
Signed-off-by: NAbhi Das <adas@redhat.com>
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>

fs/gfs2/bmap.c

@@ -1040,7 +1040,7 @@ static int trunc_start(struct gfs2_inode *ip, u64 size)
 		goto out;
 
 	if (gfs2_is_stuffed(ip)) {
-		u64 dsize = size + sizeof(struct gfs2_inode);
+		u64 dsize = size + sizeof(struct gfs2_dinode);
 		ip->i_disksize = size;
 		ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
 		gfs2_trans_add_bh(ip->i_gl, dibh, 1);