hw/arm/sbsa-ref : allocate IRQs for SMMUv3

hw/arm/sbsa-ref : allocate IRQs for SMMUv3

Original commit did not allocate IRQs for the SMMUv3 in the irqmap
effectively using irq 0->3 (shared with other devices). Assuming
original intent was to allocate unique IRQs then add an allocation
to the irqmap.

Fixes: e9fdf453240 ("hw/arm: Add arm SBSA reference machine, devices part")
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Graeme Gregory <graeme@nuviainc.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-id: 20201007100732.4103790-3-graeme@nuviainc.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>