net: netcp: ethss: use macro for checking ss_version consistently

Driver currently uses macro for NU and XBE hardwrae, while other
places for older hardware such as that on K2H/K SoC (version 1.4
of the cpsw hardware, it explicitly check for the ss_version
inline. Add a new macro for version 1.4 and use it to customize
code in the driver. While at it also fix similar issue with
checking XBE version by re-using existing macro IS_SS_ID_XGBE().

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>