clk: fixed-factor: add clk_hw_register_fixed_factor_index() function

Add non-devres version of clk_hw_register_fixed_factor(), with parent
targeted using its index.

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://lore.kernel.org/r/20241106-mbly-clk-v2-3-84cfefb3f485@bootlin.com


Signed-off-by: Stephen Boyd <sboyd@kernel.org>