drm/amd/display: link_status not align when power off encoder

[Why]
The link_status is incorrect cause driver power off eDP when backlight
on. Some eDP panels may show garbage on screen.

[How]
Correct link_status when power off encoder

Signed-off-by: Paul Hsieh <paul.hsieh@amd.com>
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>