e1000e: disable K1 on PCH LOM when in PHY loopback mode

When performing the ethtool PHY loopback test on PCH-based LOMs (82577 and
82578), disable K1 (a MAC-PHY interconnect low power mode) otherwise
packets might get corrupted.

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/e1000.h b/drivers/net/e1000e/e1000.h
index 00989c5..a6c6803 100644
--- a/drivers/net/e1000e/e1000.h
+++ b/drivers/net/e1000e/e1000.h
@@ -485,6 +485,7 @@
 extern void e1000e_igp3_phy_powerdown_workaround_ich8lan(struct e1000_hw *hw);
 extern void e1000e_gig_downshift_workaround_ich8lan(struct e1000_hw *hw);
 extern void e1000e_disable_gig_wol_ich8lan(struct e1000_hw *hw);
+extern s32 e1000_configure_k1_ich8lan(struct e1000_hw *hw, bool k1_enable);
 
 extern s32 e1000e_check_for_copper_link(struct e1000_hw *hw);
 extern s32 e1000e_check_for_fiber_link(struct e1000_hw *hw);