clk: meson: Support PLL with fixed fractional denominators

Some PLLS with fractional multipliers have fractional denominators with
fixed values, instead of the previous "(1 << pll-> frc.width)".

Signed-off-by: Chuan Liu <chuan.liu@amlogic.com>
Link: https://lore.kernel.org/r/20240909-fix_clk-v3-1-a6d8f6333c04@amlogic.com


Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>