ARM: dts: renesas: Add missing ADV751[13] power supply properties

make dtbs_check:

    arch/arm/boot/dts/renesas/r8a7791-koelsch.dtb: hdmi@39: 'avdd-supply' is a required property
	    from schema $id: http://devicetree.org/schemas/display/bridge/adi,adv7511.yaml#
    arch/arm/boot/dts/renesas/r8a7791-koelsch.dtb: hdmi@39: 'dvdd-supply' is a required property
	    from schema $id: http://devicetree.org/schemas/display/bridge/adi,adv7511.yaml#
    arch/arm/boot/dts/renesas/r8a7791-koelsch.dtb: hdmi@39: 'pvdd-supply' is a required property
	    from schema $id: http://devicetree.org/schemas/display/bridge/adi,adv7511.yaml#
    arch/arm/boot/dts/renesas/r8a7791-koelsch.dtb: hdmi@39: 'dvdd-3v-supply' is a required property
	    from schema $id: http://devicetree.org/schemas/display/bridge/adi,adv7511.yaml#
    arch/arm/boot/dts/renesas/r8a7791-koelsch.dtb: hdmi@39: 'bgvdd-supply' is a required property
	    from schema $id: http://devicetree.org/schemas/display/bridge/adi,adv7511.yaml#


    ...

Fix this by adding the missing power supply properties, and by adding
fixed regulators where needed.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/6c49fd83d327a68040f052bd9fd96fe25b0fc301.1698068647.git.geert+renesas@glider.be