Fix for ernie3.0 int8 (#43992)

* Fix for ernie3.0 int8

* Move changes above comment

paddle/fluid/operators/mkldnn/fc_mkldnn_op.cc

@@ -170,6 +170,9 @@ class FCPrimitiveFactory {
     // In case of 2 dims, we set the only possible format, nc
     if (dim_num == 2) {
       out->set_format(MKLDNNMemoryFormat::nc);
+      out->set_mem_desc({phi::vectorize(out->dims()),
+                         platform::MKLDNNGetDataType<T_out>(),
+                         out->format()});
       // In case of 3 dims, we generate a format that is based on number
       // of output dims and the layout of input format (nchw or nhwc).
     } else if (dim_num == 3) {
@@ -185,9 +188,6 @@ class FCPrimitiveFactory {
     } else {
       out->set_format(in_format);
     }
-    out->set_mem_desc({phi::vectorize(out->dims()),
-                       platform::MKLDNNGetDataType<T_out>(),
-                       out->format()});
   }
 
   void UpdateDataPointers(const ExecutionContext& ctx,