net/mlx5: fs, add HWS flow group API functions

Add API functions to create and destroy HW Steering flow groups. Each
flow group consists of a Backward Compatible (BWC) HW Steering matcher
which holds the flow group match criteria.

Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20250109160546.1733647-4-tariqt@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>