[GFS2] re-support special inode

a previous commit removed call to
init_special_inode from inode lookuping, this cause problems as:

 # mknod /mnt/gfs2/dev/null c 1 3
 # cat /mnt/gfs2/dev/null
 cat: /mnt/gfs2/dev/null: Invalid argument

without special inode, GFS2 cannot support char device file,
block device file, fifo pipe, and socket file, lose many important
features as a common file system.

this one line patch re add special inode support.
Signed-off-by: NDenis Cheng <crquan@gmail.com>
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>

fs/gfs2/inode.c

@@ -150,6 +150,7 @@ void gfs2_set_iop(struct inode *inode)
 		inode->i_op = &gfs2_symlink_iops;
 	} else {
 		inode->i_op = &gfs2_file_iops;
+		init_special_inode(inode, inode->i_mode, inode->i_rdev);
 	}
 
 	unlock_new_inode(inode);