samples: button: Enable PM Mode 3 on NXP RD_RW612

Enable testing this sample with PM Mode 3

Signed-off-by: Mahesh Mahadevan <[email protected]>

Author: mmahadevan108

samples/basic/button/boards/rd_rw612_bga.conf

@@ -0,0 +1,6 @@
+#
+# Copyright 2025 NXP
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+CONFIG_PM=y

samples/basic/button/boards/rd_rw612_bga.overlay

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2025 NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&standby {
+	status = "okay";
+};