Buffer delayed CSR result data when XIF result is not ready

If a CSR result with delayed result data cannot be transmitted to the
main core in the cycle after the result was received, then the result
data needs to be buffered as well.

rtl/vproc_result.sv

@@ -113,6 +113,14 @@ module vproc_result #(
         result_csr_delayed_d = result_csr_delayed_q;
         result_csr_data_d    = result_csr_data_q;
 
+        // for a delayed result the data is always available in the cycle after the result was
+        // received, but if the interface is not ready to return that result yet, the data has to
+        // be buffered as well
+        if (result_csr_delayed_q) begin
+            result_csr_delayed_d = 1'b0;
+            result_csr_data_d    = result_csr_data_i;
+        end
+
         if (result_source == RESULT_SOURCE_EMPTY_BUF) begin
             // clear the lowest index ID if the XIF interface is ready
             for (int i = 0; i < XIF_ID_CNT; i++) begin