devlink: pass devlink_port pointer to ops->port_del() instead of index

Historically there was a reason why port_dev() along with for example
port_split() did get port_index instead of the devlink_port pointer.
With the locking changes that were done which ensured devlink instance
mutex is hold for every command, the port ops could get devlink_port
pointer directly. Change the forgotten port_dev() op to be as others
and pass devlink_port pointer instead of port_index.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>