soc: mediatek: add dependent clock jpgdec/audio for scpsys

There are dependent clock jpgdec/audio in scpsys on MT2712,
and will exist three dependent clocks on MT2712 VDEC.

Signed-off-by: Weiyi Lu <weiyi.lu@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>