janitor: add guards to headers

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hw/cris-boot.h b/hw/cris-boot.h
index 5b17d83..c4d3fa6 100644
--- a/hw/cris-boot.h
+++ b/hw/cris-boot.h
@@ -1,3 +1,5 @@
+#ifndef _CRIS_BOOT_H
+#define HW_CRIS_BOOT_H 1
 
 struct cris_load_info
 {
@@ -9,3 +11,5 @@
 };
 
 void cris_load_image(CRISCPU *cpu, struct cris_load_info *li);
+
+#endif