binman: Fix typo in mkimage etype description

Fix a typo, no functional change.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
diff --git a/tools/binman/btool/mkimage.py b/tools/binman/btool/mkimage.py
index d5b407c..39a4c8c 100644
--- a/tools/binman/btool/mkimage.py
+++ b/tools/binman/btool/mkimage.py
@@ -11,7 +11,7 @@
     """Image generation for U-Boot
 
     This bintool supports running `mkimage` with some basic parameters as
-    neeed by binman.
+    needed by binman.
 
     Normally binman uses the mkimage built by U-Boot. But when run outside the
     U-Boot build system, binman can use the version installed in your system.