netxen: handle pci bar 0 mapping failure

PCI bar 0 is used for memory mapped register access.
If ioremap fails (returns NULL), register access results
in crash.

Use pci_ioremap_bar() instead of ioremap(), the latter
fails on on 32 bit powerpc where pci resource address is
> 32 bits.

Signed-off-by: Dhananjay Phadke <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/netxen/netxen_nic_main.c

···
 		adapter->pci_mem_read = netxen_nic_pci_mem_read_2M;
 		adapter->pci_mem_write = netxen_nic_pci_mem_write_2M;
 
-		mem_ptr0 = ioremap(mem_base, mem_len);
+		mem_ptr0 = pci_ioremap_bar(pdev, 0);
+		if (mem_ptr0 == NULL) {
+			dev_err(&pdev->dev, "failed to map PCI bar 0\n");
+			return -EIO;
+		}
+
 		pci_len0 = mem_len;
 		first_page_group_start = 0;
 		first_page_group_end   = 0;