mos6522: update counters when timer interrupts are off

Even if the interrupts are off, counters must be updated because
they are running anyway and kernel can try to read them
(it's the case with g3beige kernel).

Reported-by: Andrew Randrianasulu <randrianasulu@gmail.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20191125141414.5015-1-laurent@vivier.eu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>