ixgbe: Correct reporting of timestamping for x550

Update ixgbe_ethtool_get_ts_info() to show that x550 supports hardware
timestamping of all packets.

Reported-by: Guy Harris <guy@alum.mit.edu>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>