igb: Correct PTP support query from ethtool.

Update ethtool_get_ts_info to not report any supported functionality on
82575 and add support for V2 Sync and V2 Delay packets. In the case
where CONFIG_IGB_PTP is not defined, we should be reporting default
values.

v2: Correct the function to return EOPNOTSUPP when there is no PTP support
    or the device does not support PTP. Also fix minor whitespace issue.

Signed-off-by: Matthew Vick <matthew.vick@intel.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>