iperf: Fix license

     *the current version of Iperf has a false LICENSE set,
         so fix license with the generic BSD license

Signed-off-by: Chunrong Guo <B40290@freescale.com>
Acked-by: Paul Barker <paul@paulbarker.me.uk>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>