bnxt_en: check for ingress qdisc in flower offload

Check for ingress-only qdisc for flower offload, as other qdiscs
are not supported for flower offload.

Suggested-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Sathya Perla <sathya.perla@broadcom.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>