dt-bindings: display: Fix spacing in lvds.yaml

Add missing spaces to make the diagrams readable, no functional change.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: devicetree@vger.kernel.org
To: dri-devel@lists.freedesktop.org
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20210517224336.409301-1-marex@denx.deSigned-off-by: Rob Herring <robh@kernel.org>