soc/do_finalize: check that crg.rst is a Signal before connecting to ctrl._reset.

litex/soc/integration/soc.py

@@ -939,6 +939,7 @@ class SoC(Module):
         # Connect SoCController's reset to CRG's reset if presents.
         if hasattr(self, "ctrl") and hasattr(self, "crg"):
             if hasattr(self.ctrl, "_reset") and hasattr(self.crg, "rst"):
+                if isinstance(self.crg.rst, Signal):
                     self.comb += self.crg.rst.eq(self.ctrl._reset.re)
 
         # SoC CSR bridge ---------------------------------------------------------------------------