3com 3c515: make it compile on 64-bit architectures

This driver isn't enabled most places because of the ISA config
dependency, but alpha still has it.  And I think the 'Jensen' actually
did have an ISA slot.

However, it doesn't build cleanly, because the "Vortex bus master" code
just casts the skb->data pointer to 'int':

        outl((int) (skb->data), ioaddr + Wn7_MasterAddr);

which is all kinds of broken.  Even on a good old traditional PC/AT it
would be broken because the high bits will be random kernel address
bits, but presumably the hardware ignores those bits.  I mean, it's ISA.
We're talking 16MB dma limits. The "good old days".

Make the build happy with this kind of craziness by using the proper
isa_virt_to_bus() handling that the full bus master code uses anyway
(the Vortex bus mastering is a limited special case).

Who knows, this might even work.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/net/ethernet/3com/3c515.c

@@ -1050,7 +1050,7 @@ static netdev_tx_t corkscrew_start_xmit(struct sk_buff *skb,
 #ifdef VORTEX_BUS_MASTER
 	if (vp->bus_master) {
 		/* Set the bus-master controller to transfer the packet. */
-		outl((int) (skb->data), ioaddr + Wn7_MasterAddr);
+		outl(isa_virt_to_bus(skb->data), ioaddr + Wn7_MasterAddr);
 		outw((skb->len + 3) & ~3, ioaddr + Wn7_MasterLen);
 		vp->tx_skb = skb;
 		outw(StartDMADown, ioaddr + EL3_CMD);