Introduce typedef for vCPU index.

Change-Id: I51194706edb86811487f2a22b3bda5405e605b5e
diff --git a/src/vm.c b/src/vm.c
index 8532144..7c5166b 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -18,6 +18,7 @@
 
 #include "hf/api.h"
 #include "hf/cpu.h"
+#include "hf/spci.h"
 #include "hf/std.h"
 
 #include "vmapi/hf/call.h"
@@ -112,7 +113,7 @@
  * Get the vCPU with the given index from the given VM.
  * This assumes the index is valid, i.e. less than vm->vcpu_count.
  */
-struct vcpu *vm_get_vcpu(struct vm *vm, uint32_t vcpu_index)
+struct vcpu *vm_get_vcpu(struct vm *vm, spci_vcpu_index_t vcpu_index)
 {
 	assert(vcpu_index < vm->vcpu_count);
 	return &vm->vcpus[vcpu_index];