drm/amd/pm: enable SCPM support for SMU

With SCPM enabled, the pptable used will be signed. It cannot
be used directly by driver. To get the raw pptable, we need to
rely on the combo pptable(and its revelant SMU message).

Also, the pptable transferring(to SMU) will be performed by PSP.
Some SMU messages will be not available to driver any more.

Signed-off-by: Evan Quan <evan.quan@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>