drm/amdgpu: Rework pcie_bif ras sw_init

pcie_bif ras blocks needs to be initialized as early
as possible to handle fatal error detected in hw_init
phase. also align the pcie_bif ras sw_init with other
ras blocks

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>