hw/cpu/{a15mpcore, a9mpcore}: enable TrustZone in GIC if it is enabled in CPUs

hw/cpu/{a15mpcore, a9mpcore}: enable TrustZone in GIC if it is enabled in CPUs

If the A9 and A15 CPUs which we're creating the peripherals for have
TrustZone (EL3) enabled, then also enable it in the GIC we create.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1441383782-24378-5-git-send-email-peter.maydell@linaro.org