drm/amd/ras: use dedicated memory as vf ras command buffer

drm/amd/ras: use dedicated memory as vf ras command buffer

Use dedicated memory as vf ras command buffer.

V2:
  Add lock to ensure serialization of sending vf ras commands.

Signed-off-by: YiPeng Chai <YiPeng.Chai@amd.com>
Reviewed-by: Jinzhou Su <jinzhou.su@amd.com>
Tested-by: Jinzhou Su <jinzhou.su@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>