net/ixgbe: fix RSS RETA being reset after port start

net/ixgbe: fix RSS RETA being reset after port start

If one calls ‘rte_eth_dev_rss_reta_update’ with ixgbe before starting
the device (but after setting everything else), then RSS RETA
configuration will be zero after starting the device.

This patch gives a notification if the port not started.

Bugzilla ID: 664
Fixes: 249358424eab ("ixgbe: RSS RETA configuration")
Cc: stable@dpdk.org
Signed-off-by: Murphy Yang <murphyx.yang@intel.com>
Acked-by: Haiyue Wang <haiyue.wang@intel.com>