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 --git a/drivers/net/ethernet/intel/e1000e/e1000.h b/drivers/net/ethernet/intel/e1000e/e1000.h
index 0abc942..e78487a 100644
--- a/drivers/net/ethernet/intel/e1000e/e1000.h
+++ b/drivers/net/ethernet/intel/e1000e/e1000.h
@@ -98,6 +98,8 @@
 #define DEFAULT_RADV			8
 #define BURST_RDTR			0x20
 #define BURST_RADV			0x20
+#define PCICFG_DESC_RING_STATUS		0xe4
+#define FLUSH_DESC_REQUIRED		0x100
 
 /* in the case of WTHRESH, it appears at least the 82571/2 hardware
  * writes back 4 descriptors when WTHRESH=5, and 3 descriptors when