Initial support for upstream lfs v2.9.3

[elrafoon]

Please consider accepting this patch, as it allows depending on littlefs2-sys with current lfs version included.

There is a matching pull request in littlefs2-sys repo.

I set littlefs2-sys version to 0.2.0 for now, but that may need to be changed, depending on how the matching pull request in that crate is handled.

[elrafoon]

Matching littlefs2-sys pull request: https://github.com/trussed-dev/littlefs2-sys/pull/13