ext4: fix buffer leak in ext4_xattr_move_to_block() on error path

Fixes: 3f2571c1 ("ext4: factor out xattr moving")
Fixes: 6dd4ee7c ("ext4: Expand extra_inodes space per ...")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 2.6.23