TTY: Add definition of a new line discipline required by Amstrad E3 (Delta) ASoC driver

This patch adds new line discipline name an number to include/linux/tty.h. The
line discipline will be used by the Amstrad E3 (Delta) sound driver that will
come next in this series of patches.

Created against linux-2.6.31-rc3.
Applies to linux-omap-2.6 commit 7c5cb7862d32cb344be7831d466535d5255e35ac as
well.

Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>