drm/rockchip: lvds: do not overwrite error code

ret variable stores the return value of drm_of_find_panel_or_bridge
which can return error codes different from EPROBE_DEFER. Therefore,
let's just return that error code instead of forcing it to EPROBE_DEFER.

Fixes: 34cc0aa2

 ("drm/rockchip: Add support for Rockchip Soc LVDS")
Cc: Quentin Schulz <foss+kernel@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20231120-rk-lvds-defer-msg-v2-1-9c59a5779cf9@theobroma-systems.com