Introduce centralized quirks handling like on R-Car Gen3, and convert
the RZ/G1C SD clock table handling over to it.

This makes it easier to add more quirks later, if/when needed.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Biju Das <biju.das@bp.renesas.com>