KVM: ARM: VGIC: Optimize the vGIC vgic_update_irq_pending function.

When vgic_update_irq_pending with level-sensitive false, it is need to
deactivates an interrupt, and, it can go to out directly.
Here return a false value, because it will be not need to kick.

Signed-off-by: wanghaibin <wanghaibin.wang@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>