clk: mediatek: add pcw_chg_bit control for PLLs of MT7988

Introduce pcw_chg_bit member to struct mtk_pll_data and use it instead
of the previously hardcoded PCW_CHG_MASK macro if set.
This will needed for clocks on the MT7988 SoC.

Signed-off-by: Sam Shih <sam.shih@mediatek.com>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/3b9c65ddb08c8bedf790aacf29871af026b6f0b7.1702849494.git.daniel@makrotopia.org


Signed-off-by: Stephen Boyd <sboyd@kernel.org>