drm/amdgpu: refine the security check for RAS functions

To avoid calling RAS related functions when RAS feature isn't
supported in hardware. Change to check supported features, instead
of checking asic type.

v2: reuse amdgpu_ras_is_supported function, instead of introducing
a new flag for hardware ras feature.

Signed-off-by: Dennis Li <Dennis.Li@amd.com>
Reviewed-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Tao Zhou <tao.zhou1@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>