exfat: request to implement FITRIM ioctl for fstrim

[Ju Hyung Park]

Hi.

It has come to my attention that while exfat supports live trim via
the discard mount option, it does not implement FITRIM ioctl for
fstrim(8).

As exfat finally became the R/W cross-platform file-system solution
and many flash storages defaulting to exfat, I'd love to see fstrim
support added to exfat too.

Wentao Wang added FITRIM ioctl for vfat about 2 years ago. I hope that
can be a useful reference:
Commit f663b5b38fffeb31841f8bfaf0ef87a445b0ffee ("fat: add FITRIM
ioctl for FAT file system").

Thanks.