net/mlx5: Implement devlink total_vfs parameter

net/mlx5: Implement devlink total_vfs parameter

Some devices support both symmetric (same value for all PFs) and
asymmetric, while others only support symmetric configuration. This
implementation prefers asymmetric, since it is closer to the devlink
model (per function settings), but falls back to symmetric when needed.

Example usage:
  devlink dev param set pci/0000:01:00.0 name total_vfs value <u16> cmode permanent
  devlink dev reload pci/0000:01:00.0 action fw_activate
  echo 1 >/sys/bus/pci/devices/0000:01:00.0/remove
  echo 1 >/sys/bus/pci/rescan
  cat /sys/bus/pci/devices/0000:01:00.0/sriov_totalvfs

Signed-off-by: Vlad Dumitrescu <vdumitrescu@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Tested-by: Kamal Heib <kheib@redhat.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250907012953.301746-5-saeed@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>