KVM: arm64: GICv4.1: Allow non-trapping WFI when using HW SGIs

Just like for VLPIs, it is beneficial to avoid trapping on WFI when the
vcpu is using the GICv4.1 SGIs.

Add such a check to vcpu_clear_wfx_traps().

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20200304203330.4967-23-maz@kernel.org