drm/amdkfd: add RAS capabilities in topology for Vega20 (v2)

It is to collaborate with HSA_CAPABILITY in libhsakmt.

v2: squash in NULL pointer check

Signed-off-by: Eric Huang <JinhuiEric.Huang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>