KVM: arm64: GICv2: Don't WARN on out-of-range GICV_DIR INTID

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: GICv2: Don't WARN on out-of-range GICV_DIR INTID

vgic_v2_deactivate() passes the INTID a guest wrote to GICV_DIR straight
to vgic_get_vcpu_irq(), and treats a failed lookup as a "can't happen"
condition with WARN_ON_ONCE().

The guest can make it happen at will, though: for any INTID outside of
the implemented SGI, PPI and SPI ranges the lookup returns NULL, since
GICv2 has no LPIs. A guest running with EOImode==1 writing such an INTID
to GICV_DIR triggers the WARN, and panics hosts running with
panic_on_warn.

Drop the WARN and ignore failed lookups.