warp: README: Fix typo

Fix the spelling of 'successful'.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

board/warp/README

@@ -43,8 +43,8 @@ Transfer u-boot.imx that will be flashed into the eMMC:
 
 $ 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 ...