net: 3c509: make the array if_names static const, makes object smaller

Don't populate the array if_names on the stack but instead it
static const. Makes the object code smaller by 99 bytes.

Before:
   text    data     bss     dec     hex filename
  27886   10752     672   39310    998e ./drivers/net/ethernet/3com/3c509.o

After:
   text    data     bss     dec     hex filename
  27723   10816     672   39211    992b ./drivers/net/ethernet/3com/3c509.o

(gcc version 10.2.0)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210801152650.146572-1-colin.king@canonical.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/3com/3c509.c

@@ -514,7 +514,9 @@ static int el3_common_init(struct net_device *dev)
 {
 	struct el3_private *lp = netdev_priv(dev);
 	int err;
-	const char *if_names[] = {"10baseT", "AUI", "undefined", "BNC"};
+	static const char * const if_names[] = {
+		"10baseT", "AUI", "undefined", "BNC"
+	};
 
 	spin_lock_init(&lp->lock);