igc: Add LPI counters

Add EEE TX LPI and EEE RX LPI counters. A EEE TX LPI event
occurs when the transmitter enters EEE (IEEE 802.3az) LPI
state. A EEE RX LPI event occurs when the receiver detect
link partner entry into EEE(IEEE 802.3az) LPI state.

Signed-off-by: Sasha Neftin <sasha.neftin@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igc/igc_mac.c

@@ -307,6 +307,8 @@ void igc_clear_hw_cntrs_base(struct igc_hw *hw)
 	rd32(IGC_ICRXDMTC);
 
 	rd32(IGC_RPTHC);
+	rd32(IGC_TLPIC);
+	rd32(IGC_RLPIC);
 	rd32(IGC_HGPTC);
 	rd32(IGC_HGORCL);
 	rd32(IGC_HGORCH);

drivers/net/ethernet/intel/igc/igc_regs.h

@@ -188,6 +188,8 @@
 #define IGC_ICTXQEC	0x04118  /* Interrupt Cause Tx Queue Empty Count */
 #define IGC_ICTXQMTC	0x0411C  /* Interrupt Cause Tx Queue Min Thresh Count */
 #define IGC_RPTHC	0x04104  /* Rx Packets To Host */
+#define IGC_TLPIC	0x04148  /* EEE Tx LPI Count */
+#define IGC_RLPIC	0x0414C  /* EEE Rx LPI Count */
 #define IGC_HGPTC	0x04118  /* Host Good Packets Tx Count */
 #define IGC_RXDMTC	0x04120  /* Rx Descriptor Minimum Threshold Count */
 #define IGC_HGORCL	0x04128  /* Host Good Octets Received Count Low */