e100: Fix broken cbs accounting due to missing memset.

Alan Stern noticed that e100 caused slab corruption.
commit 98468efd changed
the allocation of cbs to use dma pools that don't return zeroed memory,
especially the cb->status field used to track which cb to clean, causing
(the visible) double freeing of skbs and a wrong free cbs count.

Now the cbs are explicitly zeroed at allocation time.
Reported-by: NAlan Stern <stern@rowland.harvard.edu>
Tested-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NRoger Oksanen <roger.oksanen@cs.helsinki.fi>
Acked-by: NJesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/e100.c

@@ -1829,6 +1829,7 @@ static int e100_alloc_cbs(struct nic *nic)
 				  &nic->cbs_dma_addr);
 	if (!nic->cbs)
 		return -ENOMEM;
+	memset(nic->cbs, 0, count * sizeof(struct cb));
 
 	for (cb = nic->cbs, i = 0; i < count; cb++, i++) {
 		cb->next = (i + 1 < count) ? cb + 1 : nic->cbs;
@@ -1837,7 +1838,6 @@ static int e100_alloc_cbs(struct nic *nic)
 		cb->dma_addr = nic->cbs_dma_addr + i * sizeof(struct cb);
 		cb->link = cpu_to_le32(nic->cbs_dma_addr +
 			((i+1) % count) * sizeof(struct cb));
-		cb->skb = NULL;
 	}
 
 	nic->cb_to_use = nic->cb_to_send = nic->cb_to_clean = nic->cbs;