net: 7990: Export lance_poll() to modules

If CONFIG_HPLANCE=m and CONFIG_NET_POLL_CONTROLLER=y:

    ERROR: "lance_poll" [drivers/net/ethernet/amd/hplance.ko] undefined!

Add the missing export to fix this.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/amd/7990.c

@@ -661,6 +661,7 @@ void lance_poll(struct net_device *dev)
 	spin_unlock(&lp->devlock);
 	lance_interrupt(dev->irq, dev);
 }
+EXPORT_SYMBOL_GPL(lance_poll);
 #endif
 
 MODULE_LICENSE("GPL");