Use spci_vm_id_t for VM IDs, and rename vm_get to vm_find.

This means that we consistently use _get for looking up by index, _find
for looking up by ID (even if the ID happens to be the same as the index
for now).

Change-Id: I54c958be771151316781f80e2057e3076fc4ae0c
diff --git a/src/cpu.c b/src/cpu.c
index 7d181dc..e35b1ec 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -122,7 +122,7 @@
 	sl_unlock(&c->lock);
 
 	if (!prev) {
-		struct vm *vm = vm_get(HF_PRIMARY_VM_ID);
+		struct vm *vm = vm_find(HF_PRIMARY_VM_ID);
 		struct vcpu *vcpu = vm_get_vcpu(vm, cpu_index(c));
 		struct vcpu_locked vcpu_locked;