clk: renesas: rcar-gen3: Allow changing the RPC[D2] clocks

clk: renesas: rcar-gen3: Allow changing the RPC[D2] clocks

I was unable to get clk_set_rate() setting a lower RPC-IF clock frequency
and that issue boiled down to me not passing CLK_SET_RATE_PARENT flag to
clk_register_composite() when registering the RPC[D2] clocks...

Fixes: db4a0073cc82 ("clk: renesas: rcar-gen3: Add RPC clocks")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Link: https://lore.kernel.org/r/be27a344-d8bf-9e0c-8950-2d1b48498496@cogentembedded.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>