drm/panel: ili9341: Correct use of device property APIs

It seems driver missed the point of proper use of device property APIs.
Correct this by updating headers and calls respectively.

Fixes: 5a042273

 ("drm/panel: Add ilitek ili9341 panel driver")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240425142706.2440113-2-andriy.shevchenko@linux.intel.com
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240425142706.2440113-2-andriy.shevchenko@linux.intel.com