igb: access to NIC time

Adds the register definitions and code to read the time
register.

Signed-off-by: John Ronciak <john.ronciak@intel.com>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc drivers/net/igb/e1000_regs.h
Simple merge

diff --cc drivers/net/igb/igb.h
Simple merge

diff --cc drivers/net/igb/igb_main.c
Simple merge