ArmVirtualizationPkg: add GICv3 detection to VirtFdtDxe

ArmVirtualizationPkg: add GICv3 detection to VirtFdtDxe

This adds support for detecting the presence of a GICv3 interrupt
controller from the device tree, and recording its distributor and
redistributor base addresses in their respective PCDs.

Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Olivier Martin <olivier.martin@arm.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16956 6f19259b-4bc3-4df7-8a09-765794883524