drm/amdgpu: process RAS fatal error MB notification

drm/amdgpu: process RAS fatal error MB notification

For RAS error scenario, VF guest driver will check mailbox
and set fed flag to avoid unnecessary HW accesses.
additionally, poll for reset completion message first
to avoid accidentally spamming multiple reset requests to host.

v2: add another mailbox check for handling case where kfd detects
timeout first

v3: set host_flr bit and use wait_for_reset

Signed-off-by: Vignesh Chander <Vignesh.Chander@amd.com>
Reviewed-by: Zhigang Luo <Zhigang.Luo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>