f2fs: choose hardlimit when softlimit is larger than hardlimit in f2fs_statfs_project()

commit 909110c060f22e65756659ec6fa957ae75777e00 upstream.

Setting softlimit larger than hardlimit seems meaningless
for disk quota but currently it is allowed. In this case,
there may be a bit of comfusion for users when they run
df comamnd to directory which has project quota.

For example, we set 20M softlimit and 10M hardlimit of
block usage limit for project quota of test_dir(project id 123).

[root@hades f2fs]# repquota -P -a