net: ethernet: ti: cpsw: move mac_hi/lo defines in cpsw.h

Move mac_hi/lo defines in common header cpsw.h and re-use
them for netcp_ethss.c.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>