drm/amdgpu: gpu recovers from fatal error in poison mode

Fatal error occurs in ras poison mode, mode1 reset
is used to recover gpu.

Signed-off-by: YiPeng Chai <YiPeng.Chai@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>