sfc: drop unnecessary list_empty

list_for_each_safe is able to handle an empty list.
The only effect of avoiding the loop is not initializing the
index variable.
Drop list_empty tests in cases where these variables are not
used.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

<smpl>
@@
expression x,e;
iterator name list_for_each_safe;
statement S;
identifier i,j;
@@

-if (!(list_empty(x))) {
   list_for_each_safe(i,j,x) S
- }
 ... when != i
     when != j
(
  i = e;
|
? j = e;
)
</smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/ptp.c

@@ -1154,7 +1154,6 @@ static void efx_ptp_drop_time_expired_events(struct efx_nic *efx)
 
 	/* Drop time-expired events */
 	spin_lock_bh(&ptp->evt_lock);
-	if (!list_empty(&ptp->evt_list)) {
 	list_for_each_safe(cursor, next, &ptp->evt_list) {
 		struct efx_ptp_event_rx *evt;
 
@@ -1166,7 +1165,6 @@ static void efx_ptp_drop_time_expired_events(struct efx_nic *efx)
 				   "PTP rx event dropped\n");
 		}
 	}
-	}
 	spin_unlock_bh(&ptp->evt_lock);
 }