clk: mediatek: mt8186-mfg: Propagate rate changes to parent

Propagate the rate changes to MFG_BG3D's parent on MT8186 to allow
for proper GPU DVFS.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20221024102307.33722-10-angelogioacchino.delregno@collabora.com


Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>