net/vmxnet3: convert to 3-Clause BSD license

net/vmxnet3: convert to 3-Clause BSD license

On behalf of the DPDK Technical board, Hemant Agrawal observed that the
DPDK project's Intellectual Property Policy (http://dpdk.org/about/charter)
requires 3-Clause BSD license or an exception approval. However, two
vmxnet3 source files have 2-Clause BSD license.

This patch modifies those licenses to 3-Clause BSD license.

Reported-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Acked-by: Cheryl Houser <chouser@vmware.com>
Acked-by: Bharat Mota <bmota@vmware.com>
Signed-off-by: Shrikrishna Khare <skhare@vmware.com>