backlight: panasonic-laptop - Fix incomplete registration failure handling

Properly return backlight registration error to parent.
Mark struct backlight_ops as const.

Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Acked-by: Harald Welte <laforge@gnumonks.org> (registration failure)
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

drivers/platform/x86/panasonic-laptop.c

@@ -352,7 +352,7 @@ static int bl_set_status(struct backlight_device *bd)
 	return acpi_pcc_write_sset(pcc, SINF_DC_CUR_BRIGHT, bright);
 }
 
-static struct backlight_ops pcc_backlight_ops = {
+static const struct backlight_ops pcc_backlight_ops = {
 	.get_brightness	= bl_get,
 	.update_status	= bl_set_status,
 };
@@ -651,8 +651,10 @@ static int acpi_pcc_hotkey_add(struct acpi_device *device)
 	props.max_brightness = pcc->sinf[SINF_AC_MAX_BRIGHT];
 	pcc->backlight = backlight_device_register("panasonic", NULL, pcc,
 						   &pcc_backlight_ops, &props);
-	if (IS_ERR(pcc->backlight))
+	if (IS_ERR(pcc->backlight)) {
+		result = PTR_ERR(pcc->backlight);
 		goto out_sinf;
+	}
 
 	/* read the initial brightness setting from the hardware */
 	pcc->backlight->props.brightness = pcc->sinf[SINF_AC_CUR_BRIGHT];