net/mlx5: enable DevX Tx queue creation

net/mlx5: enable DevX Tx queue creation

Verbs API does not support Infiniband device port number larger 255 by
design. To support more representors on a single Infiniband device DevX
API should be engaged.

While creating Send Queue (SQ) object with Verbs API, the PMD assigned
IB device port attribute and kernel created the default miss flows in
FDB domain, to redirect egress traffic from the queue being created to
representor appropriate peer (wire, HPF, VF or SF).

With DevX API there is no IB-device port attribute (it is merely kernel
one, DevX operates in PRM terms) and PMD must create default miss flows
in FDB explicitly. PMD did not provide this and using DevX API for
E-Switch configurations was disabled.

The default miss FDB flow matches E-Switch manager vport (to make sure
the source is some representor) and SQn (Send Queue number - device
internal queue index). The root flow table managed by kernel/firmware
and it does not support vport redirect action, we have to split the
default miss flow into two ones:

- flow with lowest priority in the root table that matches E-Switch
manager vport ID and jump to group 1.
- flow in group 1 that matches E-Switch manager vport ID and SQn and
forwards packet to peer vport

Signed-off-by: Xueming Li <xuemingl@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>