Added support for get_eth_**_stats() (phy/mac/ctrl) and
get_stats64()
Reused the KSZ common APIs for get_ethtool_stats() & get_sset_count()
along with relevant lan937x hooks for KSZ common layer and added
support for get_strings()
Signed-off-by: Prasanna Vengateshan <prasanna.vengateshan@xxxxxxxxxxxxx>