pinctrl: renesas: sh73a0: Share KEYIN pin group data

Pin groups keysc_in[567] are subsets of keysc_in8.

This reduces kernel size by 144 bytes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/6d11be0accdaf4a42ce2a64e64201ab0670d65db.1640269757.git.geert+renesas@glider.be