net/ethernet: Drop H8/300 Ethernet driver

Architecture is gone, so this driver is no longer needed.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>