[nrf fromtree] tests: drivers: retained_mem: add support for nRF5340 DK

nRF5340 SoC supports retained_mem driver.
Add test configuration confirming this.

Signed-off-by: Nikodem Kastelik <[email protected]>
(cherry picked from commit 34b14bb)

Author: nika-nordic

tests/drivers/retained_mem/api/boards/nrf5340dk_nrf5340_cpuapp.conf

@@ -0,0 +1 @@
+CONFIG_RETAINED_MEM_NRF_GPREGRET=n

tests/drivers/retained_mem/api/boards/nrf5340dk_nrf5340_cpuapp.overlay

@@ -0,0 +1,29 @@
+/ {
+	sram0_image@2006f000 {
+		compatible = "zephyr,memory-region", "mmio-sram";
+		reg = <0x2006f000 DT_SIZE_K(4)>;
+		zephyr,memory-region = "RetainedMem";
+		status = "okay";
+
+		retainedmem0: retainedmem {
+			compatible = "zephyr,retained-ram";
+			status = "okay";
+		};
+	};
+
+	aliases {
+		retainedmemtestdevice = &retainedmem0;
+	};
+};
+
+&gpregret1 {
+	status = "disabled";
+};
+
+&gpregret2 {
+	status = "disabled";
+};
+
+&sram0_image {
+	reg = <0x20000000 DT_SIZE_K(444)>;
+};

tests/drivers/retained_mem/api/testcase.yaml

@@ -7,6 +7,7 @@ tests:
   drivers.retained_mem.api.ram:
     platform_allow:
       - qemu_cortex_m3
+      - nrf5340dk/nrf5340/cpuapp
       - nrf54h20dk/nrf54h20/cpuapp
       - nrf54h20dk/nrf54h20/cpurad
       - nrf54l09pdk/nrf54l09/cpuapp