drm/radeon: Add module param to control CIK support

If AMDGPU supports CIK, add a module parameter to control CIK
support in radeon. It's off by default in radeon, while it will be
on by default in AMDGPU.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>