mmc: renesas_sdhi: Add r8a77470 SDHI1 support

The RZ/G1C (a.k.a. R8A77470) comes with three SDHI interfaces,
SDHI0 and SDHI2 are compatible with the R-Car Gen2 SDHIs, SDHI1
is compatible with R-Car Gen3 SDHIs and it can be used as
eMMC as well. This patch adds driver compatibility, and makes
sure both drivers get compiled for the R8A77470.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>