TTY: amiserial, stop using serial_state->{irq,type,line}

* instead of line, use tty->index or iterator...
* irq and type are left unset. So get rid of them.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>