arm64: dts: renesas: r8a7795-salvator-x: Enable HDMI outputs

Enable the HDMI encoders for the H3 Salvator-X board. The number of
encoders varies between the H3 and M3-W SoCs, so they can't be enabled
in the common salvator-x.dtsi file.

Signed-off-by: Koji Matsuoka <koji.matsuoka.xm@renesas.com>
Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>