They now live under trezor.ui.components.tt. Later
trezor.ui.components.t1 will be added and application code will be
rewritten to not use them directly in order to work on both TT and T1.
expose ff.c constants, raise them as arguments to FatFSError
introduce NotMounted and NoFilesystem as subclasses of FatFSError with
the appropriate error code set
It is possible to call `ensure_sdcard` in a way that requires only SD
card be inserted, but not necessarily formatted.
This is useful for SD-protect and possibly other use-cases where the SD
card is read-only, and "not formatted" is identical to "not containing
the right files".
