RDMA/mlx5: Fix mutex unlocking on error flow for steering anchor creation

The mutex was not unlocked on some of the error flows.
Moved the unlock location to include all the error flow scenarios.

Fixes: e1f4a52a

 ("RDMA/mlx5: Create an indirect flow table for steering anchor")
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Hamdan Igbaria <hamdani@nvidia.com>
Link: https://lore.kernel.org/r/1244a69d783da997c0af0b827c622eb00495492e.1695203958.git.leonro@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>