drm/amdgpu: add new ras workflow control flags

add ras post init function.
Do some initialization after all IP have finished their late init.

Add new member flags which will control the ras work flow.
For now, vbios enable ras for us on boot. That might change in the
future.
So there should be a flag from vbios to tell us if ras is enabled or not
on boot. Looks like there is no such info now.

Other bits of the flags are reserved to control other parts of ras.

Signed-off-by: xinhui pan <xinhui.pan@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>