net/iavf: fix data path selection

net/iavf: fix data path selection

If PF driver don't support a flex Rx descriptor that required by VF,
legacy descriptor format will be negotiated to configure the hardware
queue.

The patch fixes the issue that an Rx data path that handle flexible
descriptor  (e.g.:
iavf_recv_scattered_pkts_vec_avx512_flex_rxd) is selected while the
actual hardware queues are configured as legacy due to above scenario,
which will cause following coredump.

Fixes: 12b435bf8f2f ("net/iavf: support flex desc metadata extraction")
Cc: stable@dpdk.org
Signed-off-by: Yiding Zhou <yidingx.zhou@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>