ath79: dts: fortinet_loader: extract common part

In preparation for FAP-220-B support, rename ar934x_fortinet_loader.dtsi
to arxxxx_fortinet_loader.dtsi, to avoid confusion, as FAP-220-B shares
flash layout with FAP-221-B exactly despite different SoC.

While at that, add a label to U-boot partition to allow for nvmem MAC
binding in future.

Signed-off-by: Lech Perczak <[email protected]>

target/linux/ath79/dts/ar9344_fortinet_ap-dual.dtsi

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 
 #include "ar9344.dtsi"
-#include "ar934x_fortinet_loader.dtsi"
+#include "arxxxx_fortinet_loader.dtsi"
 
 #include <dt-bindings/gpio/gpio.h>
 #include <dt-bindings/input/input.h>

target/linux/ath79/dts/ar934x_fortinet_loader.dtsi → target/linux/ath79/dts/arxxxx_fortinet_loader.dtsi

@@ -36,7 +36,7 @@
 			#address-cells = <1>;
 			#size-cells = <1>;
 
-			partition@0 {
+			uboot: partition@0 {
 				label = "u-boot";
 				reg = <0x000000 0x040000>;
 				read-only;