tty/serial: Add support for Altera serial port

Add support for Altera 8250/16550 compatible serial port.

Signed-off-by: Ley Foon Tan <lftan@altera.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>