Use a 32 bit bitwise 'and' in SimpleHash lookup

A bit faster on 32 bits machines, more similar to
TranspositionTable::first_entry() and same result.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/tt.h

@@ -60,7 +60,7 @@ public:
 
   ~SimpleHash() { delete [] entries; }
 
-  Entry* find(Key key) const { return entries + unsigned(key & (HashSize - 1)); }
+  Entry* find(Key key) const { return entries + ((uint32_t)key & (HashSize - 1)); }
 
 protected:
   Entry* entries;