cxl/cdat: Handle cdat table build errors

The callback for building CDAT tables may return negative error codes.
This was previously unhandled and will result in potentially huge
allocations later on in ct3_build_cdat()

Detect the negative error code and defer cdat building.

Fixes: f5ee7413d592 ("hw/mem/cxl-type3: Add CXL CDAT Data Object Exchange")
Cc: Huai-Cheng Kuo <hchkuo@avery-design.com.tw>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20240126120132.24248-2-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/cxl/cxl-cdat.c

@@ -63,7 +63,7 @@ static void ct3_build_cdat(CDATObject *cdat, Error **errp)
     cdat->built_buf_len = cdat->build_cdat_table(&cdat->built_buf,
                                                  cdat->private);
 
-    if (!cdat->built_buf_len) {
+    if (cdat->built_buf_len <= 0) {
         /* Build later as not all data available yet */
         cdat->to_update = true;
         return;