enic: fix location of vnic dev unregister in enic_probe cleanup code

The vnic_dev_unregister is erroneously under CONFIG_PCI_IOV. This patch moves
it out of CONFIG_PCI_IOV

Signed-off-by: Roopa Prabhu <roprabhu@cisco.com>
Signed-off-by: Christian Benvenuti <benve@cisco.com>
Signed-off-by: Sujith Sankar <ssujith@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>