e1000e: fix flush_desc_ring implementation

The indication that a descriptor ring flush is required was read from
FEXTNVM7 by mistake. It should be read from the PCI config space.

Signed-off-by: Yanir Lubetkin <yanirx.lubetkin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

diff --cc drivers/net/ethernet/intel/e1000e/e1000.h
Simple merge

diff --cc drivers/net/ethernet/intel/e1000e/ich8lan.h
Simple merge

diff --cc drivers/net/ethernet/intel/e1000e/netdev.c
Simple merge