[APU] XMA register table cleanup, documentation.

- [APU] Clean up XMA register table.
- [APU] Document observed register ranges in the XMA register table.

src/xenia/apu/xma_register_file.h

@@ -2,7 +2,7 @@
  ******************************************************************************
  * Xenia : Xbox 360 Emulator Research Project                                 *
  ******************************************************************************
- * Copyright 2014 Ben Vanik. All rights reserved.                             *
+ * Copyright 2021 Ben Vanik. All rights reserved.                             *
  * Released under the BSD license - see LICENSE in the root for more details. *
  ******************************************************************************
  */
@@ -16,18 +16,13 @@
 namespace xe {
 namespace apu {
 
-enum XmaRegister {
-#define XE_XMA_REGISTER(index, type, name) XE_XMA_REG_##name = index,
+struct XmaRegister {
+#define XE_XMA_REGISTER(index, name) static const uint32_t name = index;
 #include "xenia/apu/xma_register_table.inc"
 #undef XE_XMA_REGISTER
 };
 
 struct XmaRegisterInfo {
-  enum class Type {
-    kDword,
-    kFloat,
-  };
-  Type type;
   const char* name;
 };
 
@@ -38,14 +33,10 @@ class XmaRegisterFile {
   static const XmaRegisterInfo* GetRegisterInfo(uint32_t index);
 
   static const size_t kRegisterCount = (0xFFFF + 1) / 4;
-  union RegisterValue {
-    uint32_t u32;
-    float f32;
-  };
-  RegisterValue values[kRegisterCount];
+  uint32_t values[kRegisterCount];
 
-  RegisterValue& operator[](int reg) { return values[reg]; }
-  RegisterValue& operator[](XmaRegister reg) { return values[reg]; }
+  uint32_t operator[](uint32_t reg) const { return values[reg]; }
+  uint32_t& operator[](uint32_t reg) { return values[reg]; }
 };
 
 }  // namespace apu