pinctrl: renesas: r8a7779: 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/3484b3cd6b4ca19788fafc01f5ead4e067275e8d.1640269757.git.geert+renesas@glider.be