decoder/dsdiff: fix byte order bug

src/decoder/DsdLib.hxx

@@ -47,6 +47,17 @@ public:
 	}
 };
 
+class DffDsdUint64 {
+	uint32_t hi;
+	uint32_t lo;
+
+public:
+	constexpr uint64_t Read() const {
+		return (uint64_t(FromBE32(hi)) << 32) |
+			uint64_t(FromBE32(lo));
+	}
+};
+
 bool
 dsdlib_read(Decoder *decoder, InputStream &is,
 	    void *data, size_t length);

src/decoder/DsdiffDecoderPlugin.cxx

@@ -43,13 +43,13 @@
 
 struct DsdiffHeader {
 	DsdId id;
-	DsdUint64 size;
+	DffDsdUint64 size;
 	DsdId format;
 };
 
 struct DsdiffChunkHeader {
 	DsdId id;
-	DsdUint64 size;
+	DffDsdUint64 size;
 
 	/**
 	 * Read the "size" attribute from the specified header, converting it