xen/arm: gic: Do not configure affinity during routing

xen/arm: gic: Do not configure affinity during routing

The affinity of a guest IRQ is set every time the guest enable it (see
vgic_enable_irqs).

It is not necessary to set the affinity when the IRQ is routed to the
guest because Xen will never receive the IRQ until it hass been enabled
by the guest.

To keep gic_route_irq_to_{xen,guest} behaving the same way (i.e just
setting up the routing), the affinity of IRQ routed to Xen is moved into
__setup_irq.

Signed-off-by: Julien grall <julien.grall@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>