board: efm32pg_stk3402a: Add storage partition

Add storage partition to the board in order to enable testing on
nvs sample.

Signed-off-by: Christian Taedcke <hacking@taedcke.com>

boards/arm/efm32pg_stk3402a/efm32pg_stk3402a.dts

@@ -86,3 +86,22 @@
 	location-swo = <0>;
 	status = "okay";
 };
+
+&flash0 {
+	/*
+	 * For more information, see:
+	 * http://docs.zephyrproject.org/latest/guides/dts/index.html#flash-partitions
+	 */
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		/* Set 4Kb of storage at the end of the 1024Kb of flash */
+		storage_partition: partition@ff000 {
+			label = "storage";
+			reg = <0x000ff000 0x00001000>;
+		};
+
+	};
+};

boards/arm/efm32pg_stk3402a/efm32pg_stk3402a.yaml

@@ -11,6 +11,7 @@ toolchain:
 supported:
   - i2c
   - gpio
+  - nvs
 testing:
   ignore_tags:
     - net