drm: rcar-du: lvds: Fix bridge_to_rcar_lvds

Using name "bridge" for macro bridge_to_rcar_lvds argument doesn't
work when the pointer name used by the caller is not "bridge".
Rename the argument to "b" to allow for any pointer name.

While at it, fix the connector_to_rcar_lvds macro similarly.

Fixes: c6a27fa4

 ("drm: rcar-du: Convert LVDS encoder code to bridge driver")
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[Fix connector_to_rcar_lvds]
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>