drm/amdgpu: define RAS query poison mode function

1. no need to query poison mode on SRIOV guest side, host can handle it.
2. define the function to simplify code.

v2: rename amdgpu_ras_poison_mode_query to amdgpu_ras_query_poison_mode.

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