clk: mediatek: clk-apmixed: Remove unneeded __init annotation

clk: mediatek: clk-apmixed: Remove unneeded __init annotation

Remove an unneeded __init annotation from the declaration of function
mtk_clk_register_ref2usb_tx(): this avoids section mismatch warnings
during modpost phase when called from functions that have no such
annotation (useful when clocks are platform drivers).

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Miles Chen <miles.chen@mediatek.com>
Link: https://lore.kernel.org/r/20220921091455.41327-6-angelogioacchino.delregno@collabora.com
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>