lib: arm64: gic-v3: enable active less vSGIs if KVM supports

In GICv4.1 a new bit was introduced to report about SGIs which have no
active state. An example of such type of SGI is a one generated directly
by the GIC-ITS H/W which is used for direct vSGI injection. To report
about this capability by the KVM to the guest a bit named "nASSGIcap" was
allocated on GICD_TYPER2[8] and for allowing guest to request KVM to use
this feature a bit named "nASSGIreq" was allocated on GICD_CTLR[8].

With kernel boot param "kvm-arm.vgic_v4_enable" enabled and H/W support
of GICv4.1, KVM will allow use of this feature for guests configured with
vgic version gicv3-its or higher. To enable direct vSGI injection while
running vSGI tests, request KVM to use this feature.

Signed-off-by: Sathyam Panda <sathyam.panda@arm.com>
Change-Id: I4930db4b2c51d1cf8d41c6c0ace2b8e650828204