e1000: Fix PCI enable to honor the need_ioport flag

On machine were no IO ports are assigned the call
to pci_enable_device() will fail, even if need_ioport
is false, we need to use pci_enable_device_mem() here.

Signed-off-by: Karsten Keil <kkeil@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>