Ensuring that Q_srl RTL style FIFOs never have a depth of 1 when spli…

…tting fifos in the set_fifo_depths transformation as it is unsupported and leads to backpressure issues.

src/finn/transformation/fpgadataflow/set_fifo_depths.py

@@ -539,7 +539,7 @@ def decompose_pow2(x):
     ret_final = []
     for cand_depth in ret_pass2:
         if cand_depth <= max_qsrl_depth:
-            ret_final.append((cand_depth, "rtl"))
+            ret_final.append((max(2,cand_depth), "rtl"))
         else:
             ret_final.append((cand_depth, "vivado"))