Fix max areas macro name

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/test/src/nffs_test_debug.c b/test/src/nffs_test_debug.c
index 2e2965d..ecd4c40 100644
--- a/test/src/nffs_test_debug.c
+++ b/test/src/nffs_test_debug.c
@@ -166,7 +166,7 @@
     int i;
 
     for (i = 0; nffs_current_area_descs[i].nad_length != 0; i++) {
-        if (i > NFFS_MAX_AREAS) {
+        if (i > NFFS_CONFIG_MAX_AREAS) {
             return;
         }
         area.na_offset = nffs_current_area_descs[i].nad_offset;