hw/intc/xics: Reset TYPE_ICS objects with device_cold_reset()

hw/intc/xics: Reset TYPE_ICS objects with device_cold_reset()

The realize method for the TYPE_ICS class uses qemu_register_reset()
to register a reset handler, as a workaround for the fact that
currently objects which directly inherit from TYPE_DEVICE don't get
automatically reset.  However, the reset function directly calls
ics_reset(), which is the function that implements the legacy reset
method.  This means that only the parent class's data gets reset, and
a subclass which also needs to handle reset, like TYPE_PHB3_MSI, has
to register its own reset function.

Make the TYPE_ICS reset function call device_cold_reset() instead:
this will handle reset for both the parent class and the subclass,
and will work whether the classes are using legacy reset or 3-phase
reset. This allows us to remove the reset function that the subclass
currently has to set up.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20221125115240.3005559-6-peter.maydell@linaro.org