clk: mediatek: add the option for determining PLL source clock

Since the previous setup always sets the PLL using crystal 26MHz, this
doesn't always happen in every MediaTek platform. So the patch added
flexibility for assigning extra member for determining the PLL source
clock.
Signed-off-by: Chen Zhong <chen.zhong@mediatek.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/mediatek/clk-mtk.h

@@ -218,6 +218,7 @@ struct mtk_pll_data {
 	uint32_t pcw_reg;
 	int pcw_shift;
 	const struct mtk_pll_div_table *div_table;
+	const char *parent_name;
 };
 
 void mtk_clk_register_plls(struct device_node *node,

drivers/clk/mediatek/clk-pll.c

@@ -312,7 +312,10 @@ static struct clk *mtk_clk_register_pll(const struct mtk_pll_data *data,
 	init.name = data->name;
 	init.flags = (data->flags & PLL_AO) ? CLK_IS_CRITICAL : 0;
 	init.ops = &mtk_pll_ops;
-	init.parent_names = &parent_name;
+	if (data->parent_name)
+		init.parent_names = &data->parent_name;
+	else
+		init.parent_names = &parent_name;
 	init.num_parents = 1;
 
 	clk = clk_register(NULL, &pll->hw);