be2net: refactor/cleanup vf configuration code

- use adapter->num_vfs (and not the module param) to store the actual
number of vfs created. Use the same variable to reflect SRIOV
enable/disable state. So, drop the adapter->sriov_enabled field.

- use for_all_vfs() macro in VF configuration code

- drop the "vf_" prefix for the fields of be_vf_cfg; the prefix is
redundant and removing it helps reduce line wrap

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