DiscIO: Move DecodeString to Volume.cpp

This had to be in the header back when it was templated, but 083faa8b
made it not templated.

Source/Core/DiscIO/Volume.cpp

@@ -3,10 +3,12 @@
 
 #include "DiscIO/Volume.h"
 
+#include <cstring>
 #include <functional>
 #include <map>
 #include <memory>
 #include <optional>
+#include <span>
 #include <string>
 #include <type_traits>
 #include <utility>
@@ -34,6 +36,13 @@ const IOS::ES::TicketReader Volume::INVALID_TICKET{};
 const IOS::ES::TMDReader Volume::INVALID_TMD{};
 const std::vector<u8> Volume::INVALID_CERT_CHAIN{};
 
+std::string Volume::DecodeString(std::span<const char> data) const
+{
+  // strnlen to trim null bytes
+  std::string string(data.data(), strnlen(data.data(), data.size()));
+  return GetRegion() == Region::NTSC_J ? SHIFTJISToUTF8(string) : CP1252ToUTF8(string);
+}
+
 template <typename T>
 static void AddToSyncHash(Common::SHA1::Context* context, const T& data)
 {

Source/Core/DiscIO/Volume.h

@@ -3,7 +3,6 @@
 
 #pragma once
 
-#include <cstring>
 #include <limits>
 #include <map>
 #include <memory>
@@ -14,7 +13,6 @@
 
 #include "Common/CommonTypes.h"
 #include "Common/Crypto/SHA1.h"
-#include "Common/StringUtil.h"
 #include "Common/Swap.h"
 #include "Core/IOS/ES/Formats.h"
 #include "DiscIO/Enums.h"
@@ -144,16 +142,7 @@ public:
   virtual std::array<u8, 20> GetSyncHash() const = 0;
 
 protected:
-  std::string DecodeString(std::span<const char> data) const
-  {
-    // strnlen to trim NULLs
-    std::string string(data.data(), strnlen(data.data(), data.size()));
-
-    if (GetRegion() == Region::NTSC_J)
-      return SHIFTJISToUTF8(string);
-
-    return CP1252ToUTF8(string);
-  }
+  std::string DecodeString(std::span<const char> data) const;
 
   void ReadAndAddToSyncHash(Common::SHA1::Context* context, u64 offset, u64 length,
                             const Partition& partition) const;