sh_eth: add R8A7743/5 support

Add support for the first two members of the Renesas RZ/G family, RZ/G1M/E
(also known as  R8A7743/5). The Ether core is the same as in the R-Car gen2
SoCs, so will share the code/data with them...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: David S. Miller <davem@davemloft.net>