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/vm.c b/src/vm.c
index c154eca..e9919d8 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -74,7 +74,7 @@
 	return vm_count;
 }
 
-struct vm *vm_get(uint32_t id)
+struct vm *vm_find(spci_vm_id_t id)
 {
 	/* Ensure the VM is initialized. */
 	if (id >= vm_count) {