net/mlx5: fs, move steering common function to fs_cmd.h

net/mlx5: fs, move steering common function to fs_cmd.h

As preparation for HW steering support in fs core level, move SW
steering helper function that can be reused by HW steering to fs_cmd.h.
The function mlx5_fs_cmd_is_fw_term_table() checks if a flow table is a
flow steering termination table and so should be handled by FW steering.

Reviewed-by: Yevgeny Kliteynik <kliteyn@nvidia.com>
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20240911201757.1505453-4-saeed@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>