platform/x86: panasonic-laptop: Return errno correctly in show callback

When an error occurs in sysfs show callback, we should return the errno
directly instead of formatting it as the result, which produces
meaningless output and doesn't inform the userspace of the error.

Fixes: 468f96b ("platform/x86: panasonic-laptop: Add support for battery charging threshold (eco mode)")
Fixes: d5a81d8 ("platform/x86: panasonic-laptop: Add support for optical driver power in Y and W series")
Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20241118064637.61832-3-ziyao@disroot.org
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: ziyao233

drivers/platform/x86/panasonic-laptop.c

@@ -614,8 +614,7 @@ static ssize_t eco_mode_show(struct device *dev, struct device_attribute *attr,
 		result = 1;
 		break;
 	default:
-		result = -EIO;
-		break;
+		return -EIO;
 	}
 	return sysfs_emit(buf, "%u\n", result);
 }
@@ -761,7 +760,12 @@ static ssize_t current_brightness_store(struct device *dev, struct device_attrib
 static ssize_t cdpower_show(struct device *dev, struct device_attribute *attr,
 			    char *buf)
 {
-	return sysfs_emit(buf, "%d\n", get_optd_power_state());
+	int state = get_optd_power_state();
+
+	if (state < 0)
+		return state;
+
+	return sysfs_emit(buf, "%d\n", state);
 }
 
 static ssize_t cdpower_store(struct device *dev, struct device_attribute *attr,