dt-bindings: display: renesas: dw-hdmi: Drop bogus node name suffix

Node names should not use numerical suffixes if the nodes can be
distinguished by unit-address.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>