clk: mediatek: Implement mtk_clk_unregister_fixed_clks() API

clk: mediatek: Implement mtk_clk_unregister_fixed_clks() API

mtk_clk_register_fixed_clks(), as the name suggests, is used to register
a given list of fixed rate clks. However it is lacking a counterpart
unregister API.

Implement said unregister API so that the various clock platform drivers
can utilize it to do proper unregistration, cleanup and removal.

In the header file, the register function's declaration is also
reformatted to fit code style guidelines.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Miles Chen <miles.chen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20220208124034.414635-16-wenst@chromium.org
Reviewed-by: Chun-Jie Chen <chun-jie.chen@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>