clk: mediatek: use en_mask as a pure div_en_mask

clk: mediatek: use en_mask as a pure div_en_mask

We no longer allow en_mask to be a combination of
pll_en_bit and div_en_mask, so remove pll_en_bit(bit0)
from en_mask to make en_mask a pure en_mask that only
used for pll dividers.

This commit continues the work done in commit 7cc4e1bbe300
("clk: mediatek: Fix asymmetrical PLL enable and disable
control") and commit f384c44754b7 ("clk: mediatek:
Add configurable enable control to mtk_pll_data") to
clean up en_mask(bit0) default setting.

Signed-off-by: Chun-Jie Chen <chun-jie.chen@mediatek.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Mandy Liu <mandyjh.liu@mediatek.com>
Link: https://lore.kernel.org/r/20220513073621.12923-1-mandyjh.liu@mediatek.com
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>