igb: Power down link when interface is down

This changes the behavior of the driver to power down the link
when the associated interface is down, unless management is enabled.

Signed-off-by: Nicholas Nunley <nicholasx.d.nunley@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/igb/e1000_defines.h b/drivers/net/igb/e1000_defines.h
index 6e036ae..c017150 100644
--- a/drivers/net/igb/e1000_defines.h
+++ b/drivers/net/igb/e1000_defines.h
@@ -481,6 +481,7 @@
 /* PHY Control Register */
 #define MII_CR_FULL_DUPLEX      0x0100  /* FDX =1, half duplex =0 */
 #define MII_CR_RESTART_AUTO_NEG 0x0200  /* Restart auto negotiation */
+#define MII_CR_POWER_DOWN       0x0800  /* Power down */
 #define MII_CR_AUTO_NEG_EN      0x1000  /* Auto Neg Enable */
 #define MII_CR_LOOPBACK         0x4000  /* 0 = normal, 1 = loopback */
 #define MII_CR_RESET            0x8000  /* 0 = normal, 1 = PHY reset */