tty: add the new termios2 ioctls to the compatible list.

Make them depend on TCGETS2.  If that one is implemented the rest should be
there as well.

Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>