netdevsim: fib: Remove redundant code

Fix the following coccicheck warnings:

./drivers/net/netdevsim/fib.c:874:5-8: Unneeded variable: "err". Return
"0" on line 889.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/fib.c

@@ -869,10 +869,8 @@ static int nsim_fib6_event(struct nsim_fib_data *data,
 	return err;
 }
 
-static int nsim_fib_event(struct nsim_fib_event *fib_event)
+static void nsim_fib_event(struct nsim_fib_event *fib_event)
 {
-	int err = 0;
-
 	switch (fib_event->family) {
 	case AF_INET:
 		nsim_fib4_event(fib_event->data, &fib_event->fen_info,
@@ -885,8 +883,6 @@ static int nsim_fib_event(struct nsim_fib_event *fib_event)
 		nsim_fib6_event_fini(&fib_event->fib6_event);
 		break;
 	}
-
-	return err;
 }
 
 static int nsim_fib4_prepare_event(struct fib_notifier_info *info,