ARM: GICv3: use hardware GICv3 redistributor values for Dom0

ARM: GICv3: use hardware GICv3 redistributor values for Dom0

The code to generate the DT node or MADT table for Dom0 reaches into the
domain's vGIC structure to learn the number of redistributor regions and
their base addresses.
Since those values are copied from the hardware, we can as well use
those hardware values directly when setting up the hardware domain.

This avoids the hardware GIC code to reference vGIC data structures.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
Reviewed-by: Julien Grall <julien.grall@arm.com>