ext4: fix duplicated mnt_drop_write call in EXT4_IOC_MOVE_EXT

Caused, AFAICS, by mismerge in commit ff9cb1c4 ("Merge branch
'for_linus' into for_linus_merged")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org  # 3.3+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext4/ioctl.c

@@ -268,7 +268,6 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		err = ext4_move_extents(filp, donor_filp, me.orig_start,
 					me.donor_start, me.len, &me.moved_len);
 		mnt_drop_write_file(filp);
-		mnt_drop_write(filp->f_path.mnt);
 
 		if (copy_to_user((struct move_extent __user *)arg,
 				 &me, sizeof(me)))