Use a consistent method to interpret the HID_CONTROLS pre-processor symbol throughout the code base.

lib_xua/api/xua_buffer.h

@@ -58,7 +58,7 @@ void XUA_Buffer(
             chanend c_sof,
             chanend c_aud_ctl,
             in port p_off_mclk
-#ifdef HID_CONTROLS
+#if( 0 < HID_CONTROLS )
             , chanend c_hid
 #endif
             , chanend c_aud
@@ -97,7 +97,7 @@ void XUA_Buffer_Ep(chanend c_aud_out,
             chanend c_sof,
             chanend c_aud_ctl,
             in port p_off_mclk
-#ifdef HID_CONTROLS
+#if( 0 < HID_CONTROLS )
             , chanend c_hid
 #endif
 #ifdef CHAN_BUFF_CTRL

lib_xua/api/xua_conf_default.h

@@ -425,10 +425,6 @@
 #define HID_CONTROLS       (0)
 #endif
 
-#if defined(HID_CONTROLS) && (HID_CONTROLS == 0)
-#undef HID_CONTROLS
-#endif
-
 /* @brief Defines whether XMOS device runs as master (i.e. drives LR and Bit clocks)
  *
  * 0: XMOS is I2S master. 1: CODEC is I2s master.
@@ -1177,7 +1173,7 @@ enum USBEndpointNumber_In
 #ifdef MIDI
     ENDPOINT_NUMBER_IN_MIDI,
 #endif
-#ifdef HID_CONTROLS
+#if( 0 < HID_CONTROLS )
     ENDPOINT_NUMBER_IN_HID,
 #endif
 #ifdef IAP