When the guest issues an affinity change, we need to tell the physical
ITS that we're now targetting a new vcpu.  This is done by extracting
the current mapping, updating the target, and reapplying the mapping.
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>