mos6522: record last_irq_levels in mos6522_set_irq()

To detect edge-triggered IRQs it is necessary to store the last state of each
IRQ in a last_irq_levels bitmap.

Note: this is a migration break for machines which use mos6522 instances which
are g3beige/mac99 (PPC) and q800 (m68k).

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220305150957.5053-10-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>