mmc: renesas_sdhi_internal_dmac: Whitelist r8a774a1

We need r8a774a1 to be whitelisted for SDHI to work on the RZ/G2M,
but we don't care about the revision of the SoC, so just whitelist
the generic part number.

Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>