arm64: defconfig: enable R8A77980 SoC

Enable the Renesas R-Car V3H (R8A77980) SoC in the ARM64 defconfig.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>