i40e: Correcting mutex usage in client code

Correcting the mutex usage, in client_subtask(), mutex_unlock has
to be called just before client_del_instance() since this function opens
and later closes the same mutex again.
Similarly in client_is_registered removing the mutex since it closes
the mutex twice.

This is a patch suggested by RDMA team.

Change-ID: Icce519c266e4221b8a2a72a15ba5bf01750e5852
Signed-off-by: Avinash Dayanand <avinash.dayanand@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_client.c

@@ -576,6 +576,7 @@ void i40e_client_subtask(struct i40e_pf *pf)
 			set_bit(__I40E_CLIENT_INSTANCE_OPENED, &cdev->state);
 		} else {
 			/* remove client instance */
+			mutex_unlock(&i40e_client_instance_mutex);
 			i40e_client_del_instance(pf, client);
 			atomic_dec(&client->ref_cnt);
 			continue;