boards: st: stm32n6570_dk: Instantiate ext flash controller

Instantiate a `soc-nv-flash` compatible node to allow using XSPI flash
driver as a real flash controller on NOR device.

Signed-off-by: Erwan Gouriou <[email protected]>

Author: erwango

boards/st/stm32n6570_dk/stm32n6570_dk_common.dtsi

@@ -23,7 +23,7 @@
 		zephyr,touch = &gt911;
 		spi-flash0 = &mx66uw1g45g;
 		zephyr,flash-controller = &mx66uw1g45g;
-		zephyr,flash = &mx66uw1g45g;
+		zephyr,flash = &ext_flash;
 		zephyr,code-partition = &slot0_partition;
 	};
 
@@ -406,32 +406,40 @@ zephyr_udc0: &usbotg_hs1 {
 		four-byte-opcodes;
 		status = "okay";
 
-		partitions {
-			compatible = "fixed-partitions";
-			#address-cells = <1>;
-			#size-cells = <1>;
-
-			/*
-			 * Following flash partition is dedicated to the use of bootloader
-			 */
-			boot_partition: partition@0 {
-				label = "mcuboot";
-				reg = <0x00000000 DT_SIZE_K(64)>;
-			};
-
-			slot0_partition: partition@10000 {
-				label = "image-0";
-				reg = <0x10000 DT_SIZE_K(1536)>;
-			};
-
-			slot1_partition: partition@210000 {
-				label = "image-1";
-				reg = <0x210000 DT_SIZE_K(1536)>;
-			};
-
-			storage_partition: partition@410000 {
-				label = "storage";
-				reg = <0x410000 DT_SIZE_K(64)>;
+		#address-cells = <1>;
+		#size-cells = <1>;
+		ranges = <0x0 0x70000000 DT_SIZE_M(128)>;
+
+		ext_flash: ext-flash@0 {
+			compatible = "soc-nv-flash";
+			reg = <0x0 DT_SIZE_M(128)>;
+			write-block-size = <1>;
+			erase-block-size = <DT_SIZE_K(4)>;
+
+			partitions {
+				compatible = "fixed-partitions";
+				#address-cells = <1>;
+				#size-cells = <1>;
+
+				boot_partition: partition@0 {
+					label = "mcuboot";
+					reg = <0x00000000 DT_SIZE_K(64)>;
+				};
+
+				slot0_partition: partition@10000 {
+					label = "image-0";
+					reg = <0x10000 DT_SIZE_K(1536)>;
+				};
+
+				slot1_partition: partition@210000 {
+					label = "image-1";
+					reg = <0x210000 DT_SIZE_K(1536)>;
+				};
+
+				storage_partition: partition@410000 {
+					label = "storage";
+					reg = <0x410000 DT_SIZE_K(64)>;
+				};
 			};
 		};
 	};