q800: fix mac_via RTC PRAM commands
The command byte is not decoded correctly.
This patch reworks the RTC/PRAM interface and fixes the problem.
It adds a comment before the function to explain how are encoded commands
and some trace-events to ease debugging.
Bug: https://bugs.launchpad.net/qemu/+bug/
1856549
Fixes:
6dca62a000 ("hw/m68k: add VIA support")
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <
20191219201439.84804-2-laurent@vivier.eu>