tests: drivers: flash: Add support flash/common to test MRAM

Add support test app `flash/common` to test MRAM on
Renesas ek_ra8p1, mck_ra8t2

Signed-off-by: Khoa Nguyen <khoa.nguyen.xh@renesas.com>

Author: khoa-nguyen-18

tests/drivers/flash/common/boards/ek_ra8p1_r7ka8p1kflcac_cm33.overlay

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&code_mram_cm33 {
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		storage_partition: partition@48000 {
+			label = "storage";
+			reg = <0x48000 DT_SIZE_K(32)>;
+		};
+	};
+};

tests/drivers/flash/common/boards/ek_ra8p1_r7ka8p1kflcac_cm85.overlay

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&code_mram_cm85 {
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		storage_partition: partition@98000 {
+			label = "storage";
+			reg = <0x98000 DT_SIZE_K(32)>;
+		};
+	};
+};

tests/drivers/flash/common/boards/mck_ra8t2_r7ka8t2lfecac_cm85.overlay

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2025 Renesas Electronics Corporation
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&code_mram_cm85 {
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		storage_partition: partition@98000 {
+			label = "storage";
+			reg = <0x98000 DT_SIZE_K(32)>;
+		};
+	};
+};