quota: Add more checking after reading from quota file

It would be better to do more sanity checking (eg. dqdh_entries,
block no.) for the content read from quota file, which can prevent
corrupting the quota file.

Link: https://lore.kernel.org/r/20220923134555.2623931-4-chengzhihao1@huawei.com


Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>