tests: drivers: flash stm32l4 RDP on internal flash partition

Define the storage_partition in the internal flash
instead of the external NOR qspi flash,
so the testcase can PASS on the disco_l4754_iot1 board.

Signed-off-by: Francois Ramu <[email protected]>

Author: FRASTM

tests/drivers/flash/stm32/boards/disco_l475_iot1.overlay

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2023 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/* Do not use the storage-partition of the external qspi-NOR flash */
+/delete-node/ &storage_partition;
+
+&flash0 {
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		/* Reserve 4KiB of flash for storage_partition. */
+		storage_partition: partition@f0000 {
+			label = "storage";
+			reg = <0x000f0000 DT_SIZE_K(4)>;
+		};
+	};
+};