parisc: add tty driver to PDC console

This patch adds a tty driver to the PDC console. It allows the use
of ports not supported by linux as a console (e.g. serial port on
C8000.) The tty driver will not register the ttyB device if PDC console
driver has been unregistered. This happens when the early printk
console is disabled as it has not been selected as the primary console.

Signed-off-by: Guy Martin <gmsoft@tuxicoman.be>
Signed-off-by: Kyle McMartin <kyle@redhat.com>