net/ixgbe: add support for representor ports

net/ixgbe: add support for representor ports

Add support for virtual function representor ports to the ixgbe PF
driver. When SR-IOV virtual functions devices are enabled a
corresponding representor port for each VF can be enabled in the
process in which the ixgbe PMD is running within, by specifying the
representor devargs with the list of VF ports that representors
are to be created for.

An example of the devargs which would create VF representor for virtual
functions 0,2,4,5,6 and 7 is:

-w DBDF,representor=[0,2,4-7]

Signed-off-by: Declan Doherty <declan.doherty@intel.com>
Signed-off-by: Mohammad Abdul Awal <mohammad.abdul.awal@intel.com>
Signed-off-by: Remy Horton <remy.horton@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>