sh_eth: offload RX checksum on R8A7740

The R-Mobile A1 (R8A7740) SoC manual describes the Ether MAC's RX checksum
offload the same way as it's implemented in the EtherAVB MAC...
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/sh_eth.c

@@ -670,6 +670,7 @@ static struct sh_eth_cpu_data r8a7740_data = {
 	.no_ade		= 1,
 	.xdfar_rw	= 1,
 	.csmr		= 1,
+	.rx_csum	= 1,
 	.tsu		= 1,
 	.select_mii	= 1,
 	.magic		= 1,