Remove template W param

Different W template parameters for the different statEntries are
not needed, simplify by consistently using 32.

Passed STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 21683 W: 4545 L: 4424 D: 12714
http://tests.stockfishchess.org/tests/view/5ad797550ebc595700526e59

Passed LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 110391 W: 16551 L: 16562 D: 77278
http://tests.stockfishchess.org/tests/view/5ad7a88f0ebc595700526e61

Closes https://github.com/official-stockfish/Stockfish/pull/1557

Bench: 5120532

src/search.cpp

@@ -92,7 +92,7 @@ namespace {
   // History and stats update bonus, based on depth
   int stat_bonus(Depth depth) {
     int d = depth / ONE_PLY;
-    return d > 17 ? 0 : d * d + 2 * d - 2;
+    return d > 17 ? 0 : 32 * d * d + 64 * d - 64;
   }
 
   // Skill structure is used to implement strength limit