package: replace mkdosfs with dosfstools

Closes #451

Move from old unmaintained dosfstools-2.11 (packaged as mkdosfs) to
now maintained dosfstools-3.0.3.

Allow each binary to be installed independently.

Signed-off-by: Mike Crowe <mac@mcrowe.com>
Tested-by: Will Newton <will.newton@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>