hw/intc/spapr_xive: Use device_cold_reset() instead of device_legacy_reset()

hw/intc/spapr_xive: Use device_cold_reset() instead of device_legacy_reset()

The h_int_reset() function resets the XIVE interrupt controller via
device_legacy_reset().  We know that the interrupt controller does
not have a qbus of its own, so the new device_cold_reset() function
(which resets both the device and its child buses) is equivalent here
to device_legacy_reset() and we can just switch to the new API.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20210503151849.8766-2-peter.maydell@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>