samples: usb: mass: add disk description to overlays

Add flash disk description to overlays. Specify custom flashdisk
partition for fat fs api test to match the Kconfig values, because
native posix storage partition is too small for FatFS filesystem.

Co-authored-by: Johann Fischer <[email protected]>
Signed-off-by: Tomasz Moń <[email protected]>

samples/subsys/usb/mass/boards/adafruit_feather_nrf52840.overlay

@@ -18,3 +18,12 @@
 		};
 	};
 };
+
+/ {
+	msc_disk0 {
+		compatible = "zephyr,flash-disk";
+		partition = <&storage_partition>;
+		disk-name = "NAND";
+		cache-size = <4096>;
+	};
+};

samples/subsys/usb/mass/boards/nrf52840dk_nrf52840.overlay

@@ -18,3 +18,12 @@
 		};
 	};
 };
+
+/ {
+	msc_disk0 {
+		compatible = "zephyr,flash-disk";
+		partition = <&storage_partition>;
+		disk-name = "NAND";
+		cache-size = <4096>;
+	};
+};

samples/subsys/usb/mass/boards/nrf5340dk_nrf5340_cpuapp.overlay

@@ -18,3 +18,12 @@
 		};
 	};
 };
+
+/ {
+	msc_disk0 {
+		compatible = "zephyr,flash-disk";
+		partition = <&storage_partition>;
+		disk-name = "NAND";
+		cache-size = <4096>;
+	};
+};

tests/subsys/fs/fat_fs_api/boards/native_posix.overlay

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2022 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&flashcontroller0 {
+	reg = <0x00000000 DT_SIZE_K(2048)>;
+};
+
+&flash0 {
+	reg = <0x00000000 DT_SIZE_K(2048)>;
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		flashdisk_partition: partition@0 {
+			label = "flashdisk";
+			reg = <0x00000000 0x00200000>;
+		};
+	};
+};
+
+/ {
+	storage_disk {
+		compatible = "zephyr,flash-disk";
+		partition = <&flashdisk_partition>;
+		disk-name = "NAND";
+		cache-size = <4096>;
+	};
+};