KVM: arm64: vgic-v3: Use bare refcount for VGIC LPIs

KVM: arm64: vgic-v3: Use bare refcount for VGIC LPIs

KVM's use of krefs to manage LPIs isn't adding much, especially
considering vgic_irq_release() is a noop due to the lack of sufficient
context.

Switch to using a regular refcount in anticipation of adding a
meaningful release concept for LPIs.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20250905100531.282980-3-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>