arm: remove irq from inflight, then change physical affinity

arm: remove irq from inflight, then change physical affinity

This patch fixes a potential race that could happen when
gic_update_one_lr and vgic_vcpu_inject_irq run simultaneously.

When GIC_IRQ_GUEST_MIGRATING is set, we must make sure that the irq has
been removed from inflight before changing physical affinity, to avoid
concurrent accesses to p->inflight, as vgic_vcpu_inject_irq will take a
different vcpu lock.

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