drm/amdgpu: Encapsulate all device reset info

To better organize struct amdgpu_device, keep all reset information
related fields together in a separated struct.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Reviewed-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>