arm64: dts: renesas: r8a779g0: Add SDHI node

Add a device node for the SD Card/MMC Interface on the Renesas R-Car V4H
(R8A779G0) SoC.

Based on a patch in the BSP by Takeshi Kihara.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/d2d5cf982a380699483edf7a632441628ee73183.1665558371.git.geert+renesas@glider.be