soc: mediatek: introduce a CAPS flag for scp_domain_data

Instead of adding more and more fields to scp_domain_data which get
checked in the code flow, add a caps field used for an indication the
characteristics for each SCP domain.

At present, type u8 for the caps field is selected which can satisfy the
current situation and doesn't take up extra space against type bool
previously used.

Suggested-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>