vmxnet3: Changes for vmxnet3 adapter version 2 (fwd)

Make the driver understand adapter version 2.

Cc: Rachel Lunnon <rachel_lunnon@stormagic.com>
Signed-off-by: Guolin Yang <gyang@vmware.com>
Signed-off-by: Shreyas N Bhatewara <sbhatewara@vmware.com>
Signed-off-by: David S. Miller <davem@davemloft.net>