vmxnet3: update to version 7

With all vmxnet3 version 7 changes incorporated in the vmxnet3 driver,
the driver can configure emulation to run at vmxnet3 version 7, provided
the emulation advertises support for version 7.

Signed-off-by: Ronak Doshi <doshir@vmware.com>
Acked-by: Guolin Yang <gyang@vmware.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>