Avoid including vm.h header in tests.

Bug: 115484857
Change-Id: I3145826c057d28ddab2c830361a5881e4455f016
diff --git a/inc/hf/dlog.h b/inc/hf/dlog.h
index 01dddd9..f36c428 100644
--- a/inc/hf/dlog.h
+++ b/inc/hf/dlog.h
@@ -17,8 +17,9 @@
 #pragma once
 
 #include <stdarg.h>
+#include <stddef.h>
 
-#include "vm.h"
+#include "hf/spci.h"
 
 #if DEBUG
 void dlog_enable_lock(void);
@@ -30,4 +31,4 @@
 #define vdlog(fmt, args)
 #endif
 
-void dlog_flush_vm_buffer(struct vm_locked vm);
+void dlog_flush_vm_buffer(spci_vm_id_t id, char buffer[], size_t length);