Introduce typedef for [v]CPU IDs.

Change-Id: I99988988d8ac57c688c5fd52f072357202255f18
diff --git a/src/arch/fake/hypervisor/cpu.c b/src/arch/fake/hypervisor/cpu.c
index 8542dbc..f5885fd 100644
--- a/src/arch/fake/hypervisor/cpu.c
+++ b/src/arch/fake/hypervisor/cpu.c
@@ -27,7 +27,7 @@
 }
 
 void arch_regs_reset(struct arch_regs *r, bool is_primary, spci_vm_id_t vm_id,
-		     uint64_t vcpu_id, paddr_t table)
+		     cpu_id_t vcpu_id, paddr_t table)
 {
 	/* TODO */
 	(void)is_primary;