Introduce typedef for [v]CPU IDs.

Change-Id: I99988988d8ac57c688c5fd52f072357202255f18
diff --git a/inc/hf/cpu.h b/inc/hf/cpu.h
index ca697e7..d44d68e 100644
--- a/inc/hf/cpu.h
+++ b/inc/hf/cpu.h
@@ -101,7 +101,7 @@
 /* TODO: Update alignment such that cpus are in different cache lines. */
 struct cpu {
 	/** CPU identifier. Doesn't have to be contiguous. */
-	uint64_t id;
+	cpu_id_t id;
 
 	/** Pointer to bottom of the stack. */
 	void *stack_bottom;
@@ -113,12 +113,12 @@
 	bool is_on;
 };
 
-void cpu_module_init(const uint64_t *cpu_ids, size_t count);
+void cpu_module_init(const cpu_id_t *cpu_ids, size_t count);
 
 size_t cpu_index(struct cpu *c);
 bool cpu_on(struct cpu *c, ipaddr_t entry, uintreg_t arg);
 void cpu_off(struct cpu *c);
-struct cpu *cpu_find(uint64_t id);
+struct cpu *cpu_find(cpu_id_t id);
 
 struct vcpu_locked vcpu_lock(struct vcpu *vcpu);
 void vcpu_unlock(struct vcpu_locked *locked);