pinctrl: renesas: r8a7791: Share QSPI pin group data

Pin groups qspi_data2{,_b} are subsets of qspi_data4{,_b}.

This reduces kernel size by 32 bytes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/fbfd27a143e87fdb94acec2e3fa8db9029e2c99c.1640269757.git.geert+renesas@glider.be