sockit board: Fix readme.txt

Config name has changed.

Signed-off-by: Charles Manning <cdhmanning@gmail.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/altera/sockit/readme.txt

@@ -41,10 +41,10 @@ How to build it
 Configure Buildroot
 -------------------
 
-The arrow_sockit_defconfig configuration is a minimal configuration with
+The altera_sockit_defconfig configuration is a minimal configuration with
 all that is required to bring the SoCkit :
 
-  $ make arrow_sockit_defconfig
+  $ make altera_sockit_defconfig
 
 Build everything
 ----------------