aspeed: Link SCU to the watchdog

aspeed: Link SCU to the watchdog

The ast2500 uses the watchdog to reset the SDRAM controller. This
operation is usually performed by u-boot's memory training procedure,
and it is enabled by setting a bit in the SCU and then causing the
watchdog to expire. Therefore, we need the watchdog to be able to
access the SCU's register space.

This causes the watchdog to not perform a system reset when the bit is
set. In the future it could perform a reset of the SDMC model.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190621065242.32535-1-joel@jms.id.au
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>