Because the existence of bridge->encoder has already been checked before
the simple_bridge_attach() function get called, And drm_bridge_attach()
will quit with a negative error code returned if it fails for some reasons.
Hence, it is guaranteed that the .encoder member of the drm_bridge instance
is not NULL when the tfp410_attach() function get called.

Remove the redundant checking codes "if (!bridge->encoder) { ... }".
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sui Jingfeng <sui.jingfeng@linux.dev>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240513153109.46786-3-sui.jingfeng@linux.dev