ramips: enable packet steering by default on mt7621

It provides a significant performance boost, especially with flow offloading
enabled

Signed-off-by: Felix Fietkau <nbd@nbd.name>

target/linux/ramips/mt7621/base-files/etc/uci-defaults/01_enable_packet_steering

@@ -0,0 +1,4 @@
+uci -q get network.globals.packet_steering > /dev/null || {
+	uci set network.globals.packet_steering=1
+	uci commit
+}