tests/amdgpu/ras: refine ras inject test

Ras inject test framework is invalid with original codes,
so refine it to make it work on top of kernel ras inject
feature enablement.

Signed-off-by: Dennis Li <dennis.li@amd.com>
Signed-off-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>