The commit updates driver, with changes that have appeared
since last update to version 0.14b, and applies Zephyr compatibility
patches to where required.

Origin: ELM Chan (http://elm-chan.org)
Project URL: http://elm-chan.org/fsw/ff/00index_e.html
Sources: http://elm-chan.org/fsw/ff/arc/ff15.zip


Sources package SHA256:
  9b8704000eb8823dc27314f63899d42c995c3f5e4e0be06382c98c90331e01a2

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>