clk: mediatek: Add mfg_eb as parent to mt8196 mfgpll clocks

clk: mediatek: Add mfg_eb as parent to mt8196 mfgpll clocks

All the MFGPLL require MFG_EB to be on for any operation on them, and
they only tick when MFG_EB is on as well, therefore making this a
parent-child relationship.

This dependency wasn't clear during the initial upstreaming of these
clock controllers, as it only made itself known when I could observe
the effects of the clock by bringing up a different piece of hardware.

Add a new PLL_PARENT_EN flag to mediatek's clk-pll.h, and check for it
when initialising the pll to then translate it into the actual
CLK_OPS_PARENT_ENABLE flag.

Then add the mfg_eb parent to the mfgpll clocks, and set the new
PLL_PARENT_EN flag.

Fixes: 03dc02f8c7dc ("clk: mediatek: Add MT8196 mfg clock support")
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>