drm/amdgpu: Move umc ras block init to gmc ras sw_init

Initialize umc ras block only when umc ip block
supports ras. Driver queries ras capabilities after
early_init, ras block init needs to be moved to
sw_init.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Stanley Yang <Stanley.Yang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>