build: fix incorrect GPL address from last commit

962b3eb40cc5b69d9b3d6fcc4c5d56c4d204a307 included the old GPL address.

Change-Id: I7affbdc3fc1c9251ea90796ab9eeef4d56ba4308
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1440
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>