f2fs: fix miscounted block limit in f2fs_statfs_project()

commit acdf2172172a511f97fa21ed0ee7609a6d3b3a07 upstream.

statfs calculates Total/Used/Avail disk space in block unit,
so we should translate soft/hard prjquota limit to block unit
as well.

Below testing result shows the block/inode numbers of
Total/Used/Avail from df command are all correct afer
applying this patch.

[root@localhost quota-tools]\# ./repquota -P /dev/sdb1