[why]
There are cases where more than 1 stream can be mapped to the same
surface. DML2.0 does not seem to handle these cases.

[how]
Make sure to account for the stream id when deriving the plane id. By
doing this, each plane id will be unique based on the stream id.
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Sung Joon Kim <sungkim@amd.com>
Signed-off-by: Qingqing Zhuo <Qingqing.Zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>