drm/amdgpu: Avoid use SOC15_REG_OFFSET in static const array

Handle dynamic offsets correctly in static arrays.

Acked-by: Christian Konig <christian.koenig@amd.com>
Signed-off-by: Shaoyun Liu <Shaoyun.Liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>