tools: buildman: fix typo

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/buildman/builder.py b/tools/buildman/builder.py
index 784c641..3fd4fac 100644
--- a/tools/buildman/builder.py
+++ b/tools/buildman/builder.py
@@ -979,7 +979,7 @@
 
         The summary takes the form of one line per architecture. The
         line contains deltas for each of the sections (+ means the section
-        got bigger, - means smaller). The nunmbers are the average number
+        got bigger, - means smaller). The numbers are the average number
         of bytes that a board in this section increased by.
 
         For example: