drm/amdgpu/display: Replace CONFIG_DRM_AMD_DC_DCN1_0 with CONFIG_X86

Allowing CONFIG_DRM_AMD_DC_DCN1_0 to be disabled on X86 was an
opportunity for display with Raven Ridge accidentally not working.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>