drm/rockchip: lvds: lower log severity for missing pinctrl settings

While missing lvds pinctrl is unexpected and is reported, we nevertheless
don't fail setting up the device and instead continue without explicit
pinctrl handling. So lower the log-level from error to warning to reflect
that.

Suggested-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Heiko Stuebner <heiko.stuebner@cherry.de>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20250304124418.111061-4-heiko@sntech.de