Reformat Eval::evaluate()

Non functional simplification: the goal of this patch is to make
the style in the evaluate() function similar to the rest of the code.

passed STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 95608 W: 24058 L: 24026 D: 47524
Ptnml(0-2): 292, 10379, 26396, 10479, 258
https://tests.stockfishchess.org/tests/view/616c64fd99b580bf37797e4f

closes https://github.com/official-stockfish/Stockfish/pull/3744

Non-functional change

src/evaluate.cpp

@@ -1081,33 +1081,22 @@ Value Eval::evaluate(const Position& pos) {
 
   Value v;
 
-  if (!useNNUE)
-      v = Evaluation<NO_TRACE>(pos).value();
+  // Deciding between classical and NNUE eval: for high PSQ imbalance we use classical,
+  // but we switch to NNUE during long shuffling or with high material on the board.
+
+  if (  !useNNUE
+      || abs(eg_value(pos.psq_score())) * 5 > (850 + pos.non_pawn_material() / 64) * (5 + pos.rule50_count()))
+      v = Evaluation<NO_TRACE>(pos).value();          // classical
   else
   {
-      // Scale and shift NNUE for compatibility with search and classical evaluation
-      auto  adjusted_NNUE = [&]()
-      {
-         int scale =   883
-                     + 32 * pos.count<PAWN>()
-                     + 32 * pos.non_pawn_material() / 1024;
+      int scale =   883
+                  + 32 * pos.count<PAWN>()
+                  + 32 * pos.non_pawn_material() / 1024;
 
-         Value nnue = NNUE::evaluate(pos, true) * scale / 1024;
+       v = NNUE::evaluate(pos, true) * scale / 1024;  // NNUE
 
-         if (pos.is_chess960())
-             nnue += fix_FRC(pos);
-
-         return nnue;
-      };
-
-      // If there is PSQ imbalance we use the classical eval, but we switch to
-      // NNUE eval faster when shuffling or if the material on the board is high.
-      int r50 = pos.rule50_count();
-      Value psq = Value(abs(eg_value(pos.psq_score())));
-      bool classical = psq * 5 > (850 + pos.non_pawn_material() / 64) * (5 + r50);
-
-      v = classical ? Evaluation<NO_TRACE>(pos).value()  // classical
-                    : adjusted_NNUE();                   // NNUE
+       if (pos.is_chess960())
+           v += fix_FRC(pos);
   }
 
   // Damp down the evaluation linearly when shuffling