e1000e: io_error_detected callback should return PCI_ERS_RESULT_DISCONNECT

on permanent failure

PCI drivers that implement the io_error_detected callback
should return PCI_ERS_RESULT_DISCONNECT if the state
passed in is pci_channel_io_perm_failure.  This state is not
checked in many of the network drivers.

This patch fixes the omission in the e1000e driver.

Signed-off-by: Mike Mason <mmlnx@us.ibm.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>