4410: update su-servo example

The example works after gateware fix in ARTIQ.
9d493028e5
Closes #2.

4410-4412.tex

@@ -853,7 +853,7 @@ def run(self):
     self.core.break_realtime()
     self.suservo.init()
     self.suservo.set_pgia_mu(0, 0)  # unity gain
-    self.suservo.cpld0.set_att(0, 15.)
+    self.suservo.cplds[0].set_att(0, 15.)
     self.channel.set_y(profile=0, y=0.) # Clear integrator
 \end{minted}