drm/amd/display: Fix ODM policy implementation

[WHY]
Only the leftmost ODM pipe should be offset when scaling. A previous
code change was intended to implement this policy, but a section of code
was overlooked.

Signed-off-by: Wesley Chalmers <Wesley.Chalmers@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: <stable@vger.kernel.org>