drm/drm-bridge: Drop conditionals around of_node pointers

Having conditional around the of_node pointer of the drm_bridge structure
is not necessary, since drm_bridge structure always has the of_node as its
member.

Let's drop the conditional to get a better looks, please also note that
this is following the already accepted commitments. see commit d8dfccde
("drm/bridge: Drop conditionals around of_node pointers") for reference.

Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240507180001.1358816-1-sui.jingfeng@linux.dev