qualcommax: ipq807x: ax89x: use the qca-etype tag for the QCA8337

The QCA8337 is behind PPE port 1, so with the plain QCA tag the EDMA
cannot offload the checksum or TSO of frames for lan3-lan8. Select the
qca-etype tag on its CPU port.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Julius Bairaktaris <julius@bairaktaris.de>
Link: https://github.com/openwrt/openwrt/pull/25754
Signed-off-by: Robert Marko <robimarko@gmail.com>

target/linux/qualcommax/dts/ipq8074-rt-ax89x.dts

@@ -584,6 +584,7 @@
 				reg = <0>;
 				label = "cpu";
 				ethernet = <&port_switch>;
+				dsa-tag-protocol = "qca-etype";
 				phy-mode = "rgmii-rxid";
 				phy-handle = <&qca8035>;
 			};