KVM: arm64: GICv4.1: Give a chance to save VLPI state

Before GICv4.1, we don't have direct access to the VLPI state. So
we simply let it fail early when encountering any VLPI in saving.

But now we don't have to return -EACCES directly if on GICv4.1. Let’s
change the hard code and give a chance to save the VLPI state (and
preserve the UAPI).

Signed-off-by: Shenming Lu <lushenming@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210322060158.1584-7-lushenming@huawei.com