be2net: support asymmetric rx/tx queue counts

be2net so far supported creation of RX/TX queues only in pairs.
On configs where rx and tx queue counts are different, creation of only
the lesser number of queues has been supported.

This patch now allows a combination of RX/TX-only channels along with
combined channels. N TX-queues and M RX-queues can be created with the
following cmds:
ethtool -L ethX combined N rx M-N  (when N < M)
ethtool -L ethX combined M tx N-M (when M < N)

Setting both RX-only and TX-only channels is still not supported.
It is mandatory to create atleast one combined channel.

Signed-off-by: Sathya Perla <sathya.perla@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>