tty: drop termiox user definitions

tty: drop termiox user definitions

As was concluded in a follow-up discussion of commit e0efb3168d34 (tty:
Remove dead termiox code) [1], termiox ioctls never worked, so there is
barely anyone using this interface. We can safely remove the user
definitions for this never adopted interface.

[1] https://lore.kernel.org/lkml/c1c9fc04-02eb-2260-195b-44c357f057c0@kernel.org/t/#u

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210105120239.28031-12-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>