KVM: arm64: vgic: Rationalise per-CPU irq accessor

KVM: arm64: vgic: Rationalise per-CPU irq accessor

Despite adding the necessary infrastructure to identify irq types,
vgic_get_vcpu_irq() treats GICv5 PPIs in a special way, which
impairs the readability of the code.

Use the existing irq classifiers to handle per-CPU irqs for all
vgic types, and let the normal control flow reach global interrupt
handling without any v5-specific path.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20260520091949.542365-9-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>