platform/x86: dell-uart-backlight: Use blacklight power constant

The backlight subsystem has gotten its own power constants. Replace
FB_BLANK_UNBLANK with BACKLIGHT_POWER_ON.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Hans de Goede <hansg@kernel.org>
Link: https://lore.kernel.org/r/20250715122643.137027-2-tzimmermann@suse.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: tdz

drivers/platform/x86/dell/dell-uart-backlight.c

@@ -305,7 +305,7 @@ static int dell_uart_bl_serdev_probe(struct serdev_device *serdev)
 	dev_dbg(dev, "Firmware version: %.*s\n", resp[RESP_LEN] - 3, resp + RESP_DATA);
 
 	/* Initialize bl_power to a known value */
-	ret = dell_uart_set_bl_power(dell_bl, FB_BLANK_UNBLANK);
+	ret = dell_uart_set_bl_power(dell_bl, BACKLIGHT_POWER_ON);
 	if (ret)
 		return ret;