ptp: igb: convert to the 64 bit get/set time methods.

For the 82576, the driver's clock is implemented using a timecounter,
and so with this patch that device is ready for the year 2038.

However, in the case of the i210, the device stores the number of
seconds in a 32 bit register.  Therefore, more work is needed on this
driver before the year 2038 comes around.

Compile tested only.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>