TTY: amiserial, remove IRQ_ports

They used to work as a storage for 'info' pointer used in ISRs.  They
are not really needed. Just pass the pointer through request_irq to
the handlers.

It was set to NULL and tested in the ISRs, but we do not need the
tests as we disable all the interrupts at the same places where NULL
sets were.

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