quota: minor code cleanup for v1_format_ops

It's not a functinal change, it's just for keeping
consistent coding style.

Link: https://lore.kernel.org/r/20191010130924.17697-1-cgxu519@mykernel.net


Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: Jan Kara <jack@suse.cz>