arm/arm64: KVM: vgic: switch to dynamic allocation

arm/arm64: KVM: vgic: switch to dynamic allocation

So far, all the VGIC data structures are statically defined by the
*maximum* number of vcpus and interrupts it supports. It means that
we always have to oversize it to cater for the worse case.

Start by changing the data structures to be dynamically sizeable,
and allocate them at runtime.

The sizes are still very static though.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
(cherry picked from commit c1bfb577addd4867a82c4f235824a315d5afb94a)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>