arm64: dts: renesas: Consolidate Salvator-X(S) HDMI0 handling

Now all Salvator-X(S) SoC/board combinations have support for HDMI
sound, all HDMI0 connector and sound descriptions are identical.
Replace them by shared descriptions in salvator-common.dtsi, to reduce
duplication.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/20210303140529.3941670-1-geert+renesas@glider.be

arm64: dts: renesas: Rename r8a7796* to r8a77960*

CONFIG_ARCH_R8A7796 was renamed to CONFIG_ARCH_R8A77960 in commit
39e57e14d7eaf818 ("soc: renesas: Add ARCH_R8A77960 for existing R-Car
M3-W"), to avoid confusion between R-Car M3-W (R8A77960) and R-Car M3-W+
(R8A77961).

Rename the DTS files as well, for consistency.

Note that DT binding headers, definitions, and compatible values were
not renamed, to preserve backward compatibility.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20191211131311.23661-1-geert+renesas@glider.be
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>