arm64: dts: agilex: add board compatible for N5X DK

The Intel SoCFPGA N5X SoC Development Kit is a board with
Agilex, so it needs its own compatible.
Signed-off-by: NKrzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: NDinh Nguyen <dinguyen@kernel.org>

arch/arm64/boot/dts/intel/socfpga_n5x_socdk.dts

@@ -6,6 +6,7 @@
 
 / {
 	model = "eASIC N5X SoCDK";
+	compatible = "intel,n5x-socdk", "intel,socfpga-agilex";
 
 	aliases {
 		serial0 = &uart0;