clk: renesas: rcar-gen3: Add divider support for PLL1 and PLL3

On some R-Car Gen3 SoCs (e.g. R-Car D3), PLL1 and PLL3 use a divider
value different from one.  Extend struct rcar_gen3_cpg_pll_config to handle
this.  As all multipliers and dividers are small, table size increase
can be kept limited by storing them in u8s instead of unsigned ints,
which saves ca. 0.5 KiB for a generic kernel.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>