warp: README: Fix typo

Fix the spelling of 'successful'.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/board/warp/README b/board/warp/README
index 0e1f076..db3100e 100644
--- a/board/warp/README
+++ b/board/warp/README
@@ -43,8 +43,8 @@
 
 $ sudo dfu-util -D u-boot.imx -a boot
 
-Then on the U-boot prompt the following message should be seen after a succesful
-upgrade:
+Then on the U-boot prompt the following message should be seen after a
+successful upgrade:
 
 #DOWNLOAD ... OK
 Ctrl+C to exit ...