amdgpu: Set cik/si_support to 1 by default if radeon isn't built

It was required to explicitly set these parameters to 1, even if the
radeon driver isn't built at all, which is not intuitive.

Reported-by: Shawn Starr <shawn.starr@rogers.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>