net/mlx5: SD, Do not query MPIR register if no sd_group

Unconditionally calling the MPIR query on BF separate mode yields the FW
syndrome below [1]. Do not call it unless admin clearly specified the SD
group, i.e. expressing the intention of using the multi-PF netdev
feature.

This fix covers cases not covered in
commit fca3b479 ("net/mlx5: Do not query MPIR on embedded CPU function").

[1]
mlx5_cmd_out_err:808:(pid 8267): ACCESS_REG(0x805) op_mod(0x1) failed,
status bad system state(0x4), syndrome (0x685f19), err(-5)

Fixes: 678eb448 ("net/mlx5: SD, Implement basic query and instantiation")
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Link: https://patch.msgid.link/20240808144107.2095424-2-tariqt@nvidia.com


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