igb: offer a PTP Hardware Clock instead of the timecompare method

This commit removes the legacy timecompare code from the igb driver and
offers a tunable PHC instead.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/Makefile

@@ -35,3 +35,4 @@ obj-$(CONFIG_IGB) += igb.o
 igb-objs := igb_main.o igb_ethtool.o e1000_82575.o \
 	    e1000_mac.o e1000_nvm.o e1000_phy.o e1000_mbx.o
 
+igb-$(CONFIG_IGB_PTP) += igb_ptp.o