enic: add devcmd2

devcmd is an interface for driver to communicate with fw/adaptor. It
involves writing data to hardware registers and waiting for the result.
This mechanism does not scale well. The queuing of "no wait" devcmds is
done in firmware memory rather than on the host. Firmware memory is a
rather more scarce and valuable resource than host memory. A devcmd storm
from one vf can disrupt the service on other pf/vf. The lack of flow
control allows for possible denial of server from one VM to another.

Devcmd2 uses work queue to post the devcmds, just like tx work queue. This
allows better flow control.

Initialize devcmd2, if fails we fall back to devcmd1.

Also change the driver version.

Signed-off-by: N V V Satyanarayana Reddy <nalreddy@cisco.com>
Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>