clk: mediatek: clk-apmixed: Add helper function to unregister ref2usb_tx

The ref2usb_tx clock was introduced a long time ago and, at that time,
the MediaTek clock drivers were using CLK_OF_DECLARE, so they would
never unregister.

Nowadays, unregistering clock drivers is a thing, as we're registering
them as platform_driver and allowing them to be kernel modules: add a
helper function to cleanup the ref2usb_tx clock during error handling
and upon module removal.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20220921091455.41327-8-angelogioacchino.delregno@collabora.com
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>

drivers/clk/mediatek/clk-apmixed.c

@@ -100,4 +100,13 @@ struct clk_hw *mtk_clk_register_ref2usb_tx(const char *name,
 }
 EXPORT_SYMBOL_GPL(mtk_clk_register_ref2usb_tx);
 
+void mtk_clk_unregister_ref2usb_tx(struct clk_hw *hw)
+{
+	struct mtk_ref2usb_tx *tx = to_mtk_ref2usb_tx(hw);
+
+	clk_hw_unregister(hw);
+	kfree(tx);
+}
+EXPORT_SYMBOL_GPL(mtk_clk_unregister_ref2usb_tx);
+
 MODULE_LICENSE("GPL");

drivers/clk/mediatek/clk-mtk.h

@@ -188,6 +188,7 @@ void mtk_free_clk_data(struct clk_hw_onecell_data *clk_data);
 
 struct clk_hw *mtk_clk_register_ref2usb_tx(const char *name,
 			const char *parent_name, void __iomem *reg);
+void mtk_clk_unregister_ref2usb_tx(struct clk_hw *hw);
 
 struct mtk_clk_desc {
 	const struct mtk_gate *clks;