UART: actually return the pins, not just the module. We should do this for the other peripherals as well

src/main/scala/devices/uart/UARTPeriphery.scala

@@ -29,10 +29,10 @@ trait HasPeripheryUARTBundle {
     uarts.foreach { _.rxd := UInt(1) }
   }
 
-  def UARTtoGPIOPins(syncStages: Int = 0): Seq[UARTGPIOPort] = uarts.map { u =>
+  def UARTtoGPIOPins(syncStages: Int = 0): Seq[UARTPinsIO] = uarts.map { u =>
     val pin = Module(new UARTGPIOPort(syncStages))
     pin.io.uart <> u
-    pin
+    pin.io.pins
   }
 }