staging: fsl-dpaa2/eth: add the get_ts_info interface for ethtool

Since hardware timestmaping has been supported in driver, this
patch is to add the get_ts_info interface for ethtool to show
timestamping capability.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>