net/mlx5: Set SMFS as a default steering mode if device supports it

Set SMFS (SW-managed flow steering) as a default steering mode
instead of DMFS (device-managed flow steering)

In SMFS, the driver writes the STEs (Steering Table Entries) directly
to the device's ICM, which allows for a higher rule insertion rate
than through using FW command interface, as it is done in DMFS.

SMFS/DMFS steering modes can be configured through devlink param
'flow_steering_mode'. The possible values are 'smfs' or 'dmfs'.
The desired 'flow_steering_mode' param value should be set before
enabling switchdev mode.

Example:

  # devlink dev param set pci/0000:05:00.0 name flow_steering_mode smfs
  # devlink dev eswitch set pci/0000:05:00.0 mode switchdev

Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>