ARM: new VGIC: Add data structure definitions

ARM: new VGIC: Add data structure definitions

Add a new header file for the new and improved GIC implementation.
The big change is that we now have a struct vgic_irq per IRQ instead
of spreading all the information over various bitmaps in the ranks.

We include this new header conditionally from within the old header
file for the time being to avoid touching all the users.

This is based on Linux commit b18b57787f5e, written by Christoffer Dall.

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