freescale: ethernet: remove unnecessary unlikely()

Both WARN_ON() and WARN_ONCE() already contain an unlikely(), so it's not
necessary to wrap it into another.

Signed-off-by: Igor Stoppa <igor.stoppa@huawei.com>
Cc: Madalin Bucur <madalin.bucur@nxp.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>