net: phy: micrel: make *-skew-ps check more lenient

It seems reasonable to fine-tune only some of the skew values when using
one of the rgmii-*id PHY modes, and even when all skew values are
specified, using the correct ID PHY mode makes sense for documentation
purposes. Such a configuration also appears in the binding docs in
Documentation/devicetree/bindings/net/micrel-ksz90x1.txt, so the driver
should not warn about it.
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Link: https://lore.kernel.org/r/20211012103402.21438-1-matthias.schiffer@ew.tq-group.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/micrel.c

@@ -863,9 +863,9 @@ static int ksz9031_config_init(struct phy_device *phydev)
 				MII_KSZ9031RN_TX_DATA_PAD_SKEW, 4,
 				tx_data_skews, 4, &update);
 
-		if (update && phydev->interface != PHY_INTERFACE_MODE_RGMII)
+		if (update && !phy_interface_is_rgmii(phydev))
 			phydev_warn(phydev,
-				    "*-skew-ps values should be used only with phy-mode = \"rgmii\"\n");
+				    "*-skew-ps values should be used only with RGMII PHY modes\n");
 
 		/* Silicon Errata Sheet (DS80000691D or DS80000692D):
 		 * When the device links in the 1000BASE-T slave mode only,