net/mlx5: Move fw reset unload to mlx5_fw_reset_complete_reload

Refactor fw reset code to have the unload driver part done on
mlx5_fw_reset_complete_reload(), so if it was called by the PF which
initiated the reload fw activate flow, the unload part will be handled
by the mlx5_devlink_reload_fw_activate() callback itself and not by the
reset event work.

This will be used by the downstream patch to invoke devlink reload
callbacks with devlink lock held.

Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>