KVM: arm64: Use the known cpu id instead of smp_processor_id()

In kvm_arch_vcpu_load(), it has the parameter cpu which is the value of
smp_processor_id(), so no need to get it again. Simply replace it.

Signed-off-by: Shaoqin Huang <shahuang@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230727090754.1900310-1-shahuang@redhat.com