pinctrl: renesas: r8a77970: Share RPC pin group data

Pin groups qspi[01]_data[24] are subsets of rpc_data.
Pin group rpc_clk1 is a subset of rpc_clk2.

This reduces kernel size by 104 bytes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/a71da3daa818a33c1e81bff07d643d3f30ff1b7d.1640269757.git.geert+renesas@glider.be