drm/amd/display: Fix the display corruption issue on Navi10

[Why]
Screen corruption on Navi10 card

[How]
Set system context in DCN only on Renoir

Tested-by: Matt Coffin <mcoffin13@gmail.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Yifan Zhang <yifan1.zhang@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>