q800: move VIA1 IRQ from level 1 to level 6

q800: move VIA1 IRQ from level 1 to level 6

On a Quadra 800 machine Linux sets via_alt_mapping to 1 and clears port B bit 6 to
ensure that the VIA1 IRQ is delivered at level 6 rather than level 1. Even though
QEMU doesn't yet emulate this behaviour, Linux still installs the VIA1 level 1 IRQ
handler regardless of the value of via_alt_mapping which is why the kernel has been
able to boot until now.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20211020134131.4392-3-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>