Apart from a dai_link_list variable, the mtk_sof_priv currently holds
data that never gets modified during runtime.
Constify the mtk_sof_priv structure and move the SOF dai_link_list as
sof_dai_link_list in struct mtk_soc_card_data, which is a structure
that already holds the card's machine specific, runtime modified data.
This allows to safely pass the mtk_sof_priv structure as platform data
for the commonized card probe mechanism.