net/mlx5: devlink, Only show PF related devlink warning when needed

Limit the PF related warning to show if device is actually a PF.

Signed-off-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Maor Dickman <maord@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>