FROMLIST: clk: clk-fractional-divider: Export clk_fractional_divider_general_approximation API

This is used by the Rockchip clk driver, export it to allow that
driver to be compiled as a module.

Bug: 300024866
Change-Id: Ie457e795b105312aeb220b6070972d50a07797d9
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Link: https://lore.kernel.org/lkml/20230801081456.2551-1-zhangqing@rock-chips.com/