ELM FatFS implementation supports LFN, enabled via ffconf.h
configuration file. Additionally, code page (character set),
max file name length, and memory mode (LFN working buffer location)
are configurable options closely related to LFN.
Without LFN filenames are restricted to 8.3 filename format.
Add kconfig options to expose following FatFS configurations:
enable LFN, specify max filename length, specify code page
(character set), specify LFN working buffer location.
Signed-off-by: Audun Korneliussen <audun.korneliussen@nordicsemi.no>
917afdf89d