tools: share function to convert prio to string

No change is expected in the final binary since right now only an inline
function is shared. Later we expect to share more code.
diff --git a/tools/kmod.h b/tools/kmod.h
index 7bf6c43..ceff861 100644
--- a/tools/kmod.h
+++ b/tools/kmod.h
@@ -38,3 +38,5 @@
 
 /* kmod.c */
 extern const char *binname;
+
+#include "log.h"