ixgbe: DCB and SR-IOV can not co-exist and will cause hangs

DCB and SR-IOV cannot currently be enabled at the same time as the queueing
schemes are incompatible.  If they are both enabled it will result in Tx
hangs since only the first Tx queue will be able to transmit any traffic.

This simple fix for this is to block us from enabling TCs in ixgbe_setup_tc
if SR-IOV is enabled.  This change will be reverted once we can support
SR-IOV and DCB coexistence.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>