KVM: arm64: Fast-track kvm_mpidr_to_vcpu() when mpidr_data is available

If our fancy little table is present when calling kvm_mpidr_to_vcpu(),
use it to recover the corresponding vcpu.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Tested-by: Joey Gouly <joey.gouly@arm.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230927090911.3355209-10-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>