arm64: dts: renesas: r8a779a0: Add MMC node

Add a device node for MMC.

Signed-off-by: Takeshi Saito <takeshi.saito.xv@renesas.com>
Signed-off-by: Koji Matsuoka <koji.matsuoka.xm@renesas.com>
[wsa: double checked & rebased]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210125075845.3864-2-wsa+renesas@sang-engineering.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>