clk: mediatek: clk-mt8195-topckgen: Register mfg_ck_fast_ref as generic mux

clk: mediatek: clk-mt8195-topckgen: Register mfg_ck_fast_ref as generic mux

This clock was being registered as clk-composite through the helpers
for the same in the MediaTek clock APIs but, in reality, this isn't
a composite clock.

Appropriately register this clock with devm_clk_hw_register_mux().
No functional changes.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20220927101128.44758-7-angelogioacchino.delregno@collabora.com
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>