auxdisplay: panel: Convert to use charlcd_free()

Convert to use charlcd_free() instead of kfree() for sake of type check.
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>

drivers/auxdisplay/panel.c

@@ -1620,7 +1620,7 @@ static void panel_attach(struct parport *port)
 	if (lcd.enabled)
 		charlcd_unregister(lcd.charlcd);
 err_unreg_device:
-	kfree(lcd.charlcd);
+	charlcd_free(lcd.charlcd);
 	lcd.charlcd = NULL;
 	parport_unregister_device(pprt);
 	pprt = NULL;
@@ -1647,7 +1647,7 @@ static void panel_detach(struct parport *port)
 	if (lcd.enabled) {
 		charlcd_unregister(lcd.charlcd);
 		lcd.initialized = false;
-		kfree(lcd.charlcd);
+		charlcd_free(lcd.charlcd);
 		lcd.charlcd = NULL;
 	}