ixgbe: add support for get_ts_info

This patch adds support for the ethtool get_ts_info operation, which enables
access of available timestamp/timesync support for that device. It can query
which ptp clock device is associated with the particular port.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>