mlx5ib: mlx5_ib_create_flow returns error if udata is NULL

[vag.singh_oneconvergence.com]

Summary

[PATCH 31/31] FreeBSD OFED support for DPDK MLX5 PMD

In mlx5_ib_create_flow if udata is NULL, it returns error,
because of this, MLX5 test-pmd fails to launch.
The Linux code does not return error if udata is NULL.
This fix brings in the same behaviour.

Test Plan

Tested on KVM, ESXi, and HyperV/Azure Hypervisors with FreeBSD 14.0-CURRENT and FreeBSD12.1-STABLE.

iperf
DPDK MLX5 PMD/testpmd