[nrf fromlist] samples: boards: nordic: system_off: delay systemoff until logs are printed

Wait until console printed all data.

Upstream PR #: 81706

Signed-off-by: Piotr Kosycarz <[email protected]>

Author: nordic-piks

samples/boards/nordic/system_off/src/main.c

@@ -87,6 +87,19 @@ int main(void)
 		retained_update();
 	}
 
+	/* Wait until all logs are printed into console */
+	if (IS_ENABLED(CONFIG_PM_DEVICE) && IS_ENABLED(CONFIG_SERIAL)) {
+		static const struct device *dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_console));
+		int err;
+		enum pm_device_state state;
+
+		if (dev) {
+			do {
+				err = pm_device_state_get(dev, &state);
+			} while ((err == 0) && (state == PM_DEVICE_STATE_ACTIVE));
+		}
+	}
+
 	sys_poweroff();
 
 	return 0;