mac_via: implement ADB_STATE_IDLE state if shift register in input mode

mac_via: implement ADB_STATE_IDLE state if shift register in input mode

NetBSD switches directly to IDLE state without switching the shift register to
input mode. Duplicate the existing ADB_STATE_IDLE logic in input mode from when
the shift register is in output mode which allows the ADB autopoll handler to
handle the response.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-ID: <20231004083806.757242-17-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>