AudioInterface: Use member initializers where applicable for unions

Migrates more code to the initialization capabilities available since C++11

Source/Core/Core/HW/AudioInterface.cpp

@@ -73,8 +73,8 @@ enum
 // AI Control Register
 union AICR
 {
-  AICR() { hex = 0; }
-  AICR(u32 _hex) { hex = _hex; }
+  AICR() = default;
+  explicit AICR(u32 hex_) : hex{hex_} {}
   struct
   {
     u32 PSTAT : 1;     // sample counter/playback enable
@@ -88,20 +88,19 @@ union AICR
     u32 AIDFR : 1;     // AID Frequency (0=48khz 1=32khz)
     u32 : 25;
   };
-  u32 hex;
+  u32 hex = 0;
 };
 
 // AI Volume Register
 union AIVR
 {
-  AIVR() { hex = 0; }
   struct
   {
     u32 left : 8;
     u32 right : 8;
     u32 : 16;
   };
-  u32 hex;
+  u32 hex = 0;
 };
 
 // STATE_TO_SAVE