Removes freePort from the HAL (#116)

It was a no-op, and most likely in the future it will be that way too.
Removing to clean up the API.

wpilibj/src/athena/java/edu/wpi/first/wpilibj/AnalogOutput.java

@@ -37,7 +37,6 @@ public class AnalogOutput extends SensorBase implements LiveWindowSendable {
 
     final int portHandle = AnalogJNI.getPort((byte) channel);
     m_port = AnalogJNI.initializeAnalogOutputPort(portHandle);
-    AnalogJNI.freePort(portHandle);
 
     LiveWindow.addSensor("AnalogOutput", channel, this);
     UsageReporting.report(tResourceType.kResourceType_AnalogOutput, channel);

wpilibj/src/athena/java/edu/wpi/first/wpilibj/hal/JNIWrapper.java

@@ -62,6 +62,4 @@ public class JNIWrapper {
   public static native int getPortWithModule(byte module, byte pin);
 
   public static native int getPort(byte pin);
-
-  public static native void freePort(int halPortHandle);
 }