If these flags are advertised by a PMD, the NIC supports the MACsec
offload. The incoming MACsec traffics can be offloaded transparently
after the MACsec offload is configured correctly by the application.
And the application can set the PKT_TX_MACSEC flag in mbufs to enable
the MACsec offload for the packets to be transmitted.
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>