fdformat: remove command from default build

fdformat: remove command from default build

It should be safe assumption a command related to floppy disks does not
need to be part of default build.  Notice that the reference commit removed
floppy driver from linux about year ago.  Virtual floppies might exist they
should not need low-level formatting.  But if someone really needs this
enabling the build in that case is better than pushing the binary by
default to many many systems that install util-linux.

Reference: https://github.com/torvalds/linux/commit/47d6a7607443ea43dbc4d0f371bf773540a8f8f4
Signed-off-by: Sami Kerola <kerolasa@iki.fi>