drm/amd/display: fix build error on arm64

dcn20_build_mapped_resource() and dcn20_acquire_dsc() is not defined,
if CONFIG_DRM_AMD_DC_DCN is disabled.

Fix the following build error on arm64:

  ERROR: modpost: "dcn20_build_mapped_resource" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!
  ERROR: modpost: "dcn20_acquire_dsc" [drivers/gpu/drm/amd/amdgpu/amdgpu.ko] undefined!

Fixes: 20dad381 ("drm/amd/display: Add a helper to map ODM/MPC/Multi-Plane resources")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_resource.c

@@ -3721,12 +3721,16 @@ bool dc_resource_acquire_secondary_pipe_for_mpc_odm(
 		else
 			sec_pipe->stream_res.opp = sec_pipe->top_pipe->stream_res.opp;
 		if (sec_pipe->stream->timing.flags.DSC == 1) {
+#if defined(CONFIG_DRM_AMD_DC_DCN)
 			dcn20_acquire_dsc(dc, &state->res_ctx, &sec_pipe->stream_res.dsc, pipe_idx);
+#endif
 			ASSERT(sec_pipe->stream_res.dsc);
 			if (sec_pipe->stream_res.dsc == NULL)
 				return false;
 		}
+#if defined(CONFIG_DRM_AMD_DC_DCN)
 		dcn20_build_mapped_resource(dc, state, sec_pipe->stream);
+#endif
 	}
 
 	return true;