drm/amdgpu/display: fix dependencies for DRM_AMD_DC_SI

[ Upstream commit 4702b34d ]

Depends on DRM_AMDGPU_SI and DRM_AMD_DC

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>