Revert "drm/amdgpu/display: Replace CONFIG_DRM_AMD_DC_DCN1_0 with CONFIG_X86"

This reverts commit 8624c3c4dbfe24fc6740687236a2e196f5f4bfb0.

We need CONFIG_DRM_AMD_DC_DCN1_0 to guard code that is using fp math.

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>