pinctrl: renesas: r8a7790: Share MMC pin group data

Pin groups mmc[01]_data[14] are subsets of mmc[01]_data8.

This reduces kernel size by 80 bytes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/0990a63016ab87d16c19097bc43d79595c0c8b87.1640269757.git.geert+renesas@glider.be