airoha/dts: use nonzero bootdelay for the cases of wrongly configured boardid.

This dts are will be selected only if
 * boardid is not configured
 * boardid does not match to any of u-boot dtb

In any case, if this happen the user should have an easy way to enter
u-boot command line.

airoha/dts/en7523-basic.dts

@@ -26,6 +26,10 @@
 / {
 	model = "en75xx-arm";
 	compatible = "econet,en7523";
+
+	config {
+		bootdelay = <2>;
+	};
 };
 
 &voip {

airoha/dts/en7581-basic.dts

@@ -11,6 +11,10 @@
 / {
 	model = "EN75xx GENERIC";
 	compatible = "econet,en7581", "airoha,en7581";
+
+	config {
+		bootdelay = <2>;
+	};
 };
 
 &voip {