net: dsa: microchip: lan937x: disable in-band status support for RGMII interfaces

This driver do not support in-band mode and in case of CPU<->Switch
link, this mode is not working any way. So, disable it otherwise ingress
path of the switch MAC will stay disabled.

Note: lan9372 manual do not document 0xN301 BIT(2) for the RGMII mode
and recommend[1] to disable in-band link status update for the RGMII RX
path by clearing 0xN302 BIT(0). But, 0xN301 BIT(2) seems to work too, so
keep it unified with other KSZ switches.

[1] https://microchip.my.site.com/s/article/LAN937X-The-required-configuration-for-the-external-MAC-port-to-operate-at-RGMII-to-RGMII-1Gbps-link-speedSigned-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz_common.c

@@ -3116,7 +3116,8 @@ static void ksz_set_xmii(struct ksz_device *dev, int port,
 		/* On KSZ9893, disable RGMII in-band status support */
 		if (dev->chip_id == KSZ9893_CHIP_ID ||
 		    dev->chip_id == KSZ8563_CHIP_ID ||
-		    dev->chip_id == KSZ9563_CHIP_ID)
+		    dev->chip_id == KSZ9563_CHIP_ID ||
+		    is_lan937x(dev))
 			data8 &= ~P_MII_MAC_MODE;
 		break;
 	default: