clk: sunxi-ng: Avoid computing the rate twice

The ccu_*_find_best() functions already compute a best_rate at the same
time as the other factors. Return this value so the caller does not need
to duplicate the computation.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Link: https://lore.kernel.org/r/20221231173055.42384-1-samuel@sholland.org


Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>