hw/ppc/40p: Move the MC146818 RTC to the board where it belongs

The MC146818 RTC was incorrectly added to the i82378 chipset in
commit a04ff940974a. In the next commit (506b7ddf8893) the PReP
machine use the i82378.
Since the MC146818 is specific to the PReP machine, move its use
there.

Fixes: a04ff940974a
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190505152839.18650-3-philmd@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2 files changed