Add missing Mynewt includes

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/include/nffs/nffs.h b/include/nffs/nffs.h
index dce17df..ea50b74 100644
--- a/include/nffs/nffs.h
+++ b/include/nffs/nffs.h
@@ -578,6 +578,8 @@
 #else
 
 /* Default to Mynewt */
+#include "log/log.h"
+#include "testutil/testutil.h"
 
 #define NFFS_LOG(lvl, ...) \
     LOG_ ## lvl(&nffs_log, LOG_MODULE_NFFS, __VA_ARGS__)