be2net: Don't leak iomapped memory on removal.

The adapter->pcicfg resource is either mapped via pci_iomap() or
derived from adapter->db. During be_remove() this resource was ignored
and so could remain mapped after remove.

Add a flag to track whether adapter->pcicfg was mapped or not, then
use that flag in be_unmap_pci_bars() to unmap if required.

Fixes: 25848c90 ("use PCI MMIO read instead of config read for errors")

Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>