Fix initialization of TTData.

https://tests.stockfishchess.org/tests/view/6757757686d5ee47d9541de9
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 151200 W: 39396 L: 39306 D: 72498
Ptnml(0-2): 445, 16404, 41781, 16556, 414

Discussed in more detail here #5766

closes https://github.com/official-stockfish/Stockfish/pull/5773

No functional change

src/tt.h

@@ -51,6 +51,15 @@ struct TTData {
     Depth depth;
     Bound bound;
     bool  is_pv;
+
+    TTData() = delete;
+    TTData(Move m, Value v, Value ev, Depth d, Bound b, bool pv) :
+        move(m),
+        value(v),
+        eval(ev),
+        depth(d),
+        bound(b),
+        is_pv(pv) {};
 };