ixgbe: PTP get_ts_info missing software support

ixgbe: PTP get_ts_info missing software support

commit 50f8d35de8ba4af311ea1176c534e8b73bb198e5 upstream.

This patch corrects the ethtool get_ts_info functon which did not state that
software timestamping was supported, even though it is.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>