ixgbe: Add support for setting CC bit when SR-IOV is enabled

This change makes it so that the CC bit in the descriptor is set when
SR-IOV is enabled.  This is needed in order to support offloading
functionality when passing traffic over the internal TX switch.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>