drm/amd/display: fix double memory allocation

[Why & How]
when trying to fix a nullptr dereference on VMs,
accidentally doubly allocated memory for the non VM
case. removed the extra link_srv creation since
dc_construct_ctx is called in both VM and non VM cases
Also added a proper fail check for if kzalloc fails

Cc: stable@vger.kernel.org
Cc: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Leo Ma <Hanghong.Ma@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Martin Leung <Martin.Leung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -887,7 +887,10 @@ static bool dc_construct_ctx(struct dc *dc,
 	}
 
 	dc->ctx = dc_ctx;
+
 	dc->link_srv = link_create_link_service();
+	if (!dc->link_srv)
+		return false;
 
 	return true;
 }
@@ -986,8 +989,6 @@ static bool dc_construct(struct dc *dc,
 		goto fail;
 	}
 
-	dc->link_srv = link_create_link_service();
-
 	dc->res_pool = dc_create_resource_pool(dc, init_params, dc_ctx->dce_version);
 	if (!dc->res_pool)
 		goto fail;