tty: serial: altera_jtaguart: Support getting mapbase and IRQ from resources

This will make it easier to get the driver to support device tree. The
old platform data method is still supported though.

Also change the driver to use only one platform device per port.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>