hw/cpu/a15mpcore: If CPU has EL2, enable it on the GIC and wire it up

hw/cpu/a15mpcore: If CPU has EL2, enable it on the GIC and wire it up

For the A15MPCore internal peripheral object, we handle GIC
security extensions support by checking whether the CPUs
have EL3 enabled; if so then we enable it also on the GIC.
Handle the virtualization extensions in the same way: if the
CPU has EL2 then enable it on the GIC and wire up the
virtualization-specific memory regions and the maintenance
interrupt.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Luc Michel <luc.michel@greensocs.com>
Message-id: 20180821132811.17675-8-peter.maydell@linaro.org