sh_eth: Add R7S9210 support

Add support for the R7S9210 which is part of the RZ/A2 series.

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>