98kbd{,-io} and 98spkr all went out with PC98 subarch.  Remove stale Makefile
entries that remained.

Signed-off-by: Arthur Othieno <apgo@patchbomb.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>