[firtool] Move LowerLayers later in pipeline. (#7639)

LowerLayers belongs with the other passes that lower out of FIRRTL.

Start moving it, now that first batch of passes have been fixed
to handle enough FIRRTL IR to run in presence of layer operations.

lib/Firtool/Firtool.cpp

@@ -141,8 +141,6 @@ LogicalResult firtool::populateCHIRRTLToLowFIRRTL(mlir::PassManager &pm,
     modulePM.addPass(firrtl::createLayerSinkPass());
   }
 
-  pm.nest<firrtl::CircuitOp>().addPass(firrtl::createLowerLayersPass());
-
   pm.nest<firrtl::CircuitOp>().addPass(firrtl::createInlinerPass());
 
   // Preset the random initialization parameters for each module. The current
@@ -176,6 +174,8 @@ LogicalResult firtool::populateCHIRRTLToLowFIRRTL(mlir::PassManager &pm,
   if (!opt.shouldDisableOptimization())
     pm.nest<firrtl::CircuitOp>().addPass(firrtl::createIMConstPropPass());
 
+  pm.nest<firrtl::CircuitOp>().addPass(firrtl::createLowerLayersPass());
+
   pm.addNestedPass<firrtl::CircuitOp>(firrtl::createAddSeqMemPortsPass());
 
   pm.addPass(firrtl::createCreateSiFiveMetadataPass(