e1000e: rework disable K1 at 1000Mbps for 82577/82578

This patch reworks a previous workaround (commit 7d3cabbcc) for an issue
in hardware where noise on the interconnect between the MAC and PHY could
be generated by a lower power mode (K1) at 1000Mbps resulting in bad
packets.  Disable K1 while at 1000 Mbps but keep it enabled for 10/100Mbps
and when the cable is disconnected.  The original version of this
workaround was found to be incomplete.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/e1000e/defines.h b/drivers/net/e1000e/defines.h
index 4741ef9..1190167 100644
--- a/drivers/net/e1000e/defines.h
+++ b/drivers/net/e1000e/defines.h
@@ -76,6 +76,7 @@
 /* Extended Device Control */
 #define E1000_CTRL_EXT_SDP7_DATA 0x00000080 /* Value of SW Definable Pin 7 */
 #define E1000_CTRL_EXT_EE_RST    0x00002000 /* Reinitialize from EEPROM */
+#define E1000_CTRL_EXT_SPD_BYPS  0x00008000 /* Speed Select Bypass */
 #define E1000_CTRL_EXT_RO_DIS    0x00020000 /* Relaxed Ordering disable */
 #define E1000_CTRL_EXT_DMA_DYN_CLK_EN 0x00080000 /* DMA Dynamic Clock Gating */
 #define E1000_CTRL_EXT_LINK_MODE_MASK 0x00C00000