[hal] Add support for DMA to Java (#3158)

wpilibc/src/main/native/include/frc/PWM.h

@@ -12,6 +12,7 @@
 
 namespace frc {
 class AddressableLED;
+class DMA;
 
 /**
  * Class implements the PWM generation in the FPGA.
@@ -33,6 +34,7 @@ class AddressableLED;
 class PWM : public wpi::Sendable, public wpi::SendableHelper<PWM> {
  public:
   friend class AddressableLED;
+  friend class DMA;
   /**
    * Represents the amount to multiply the minimum servo-pulse pwm period by.
    */