Remove redundant king square parameter

We don't need to pass the king square as an explicit parameter to the functions
king_safety() and do_king_safety() since we already pass in the position.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 69686 W: 14894 L: 14866 D: 39926
http://tests.stockfishchess.org/tests/view/5be84ac20ebc595e0ae3283c

No functional change.

src/evaluate.cpp

@@ -415,7 +415,7 @@ namespace {
     Bitboard kingFlank, weak, b, b1, b2, safe, unsafeChecks;
 
     // King shelter and enemy pawns storm
-    Score score = pe->king_safety<Us>(pos, ksq);
+    Score score = pe->king_safety<Us>(pos);
 
     // Find the squares that opponent attacks in our king flank, and the squares
     // which are attacked twice in that flank but not defended by our pawns.

src/pawns.cpp

@@ -237,8 +237,9 @@ Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
 /// when king square changes, which is about 20% of total king_safety() calls.
 
 template<Color Us>
-Score Entry::do_king_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos) {
 
+  Square ksq = pos.square<KING>(Us);
   kingSquares[Us] = ksq;
   castlingRights[Us] = pos.can_castle(Us);
   int minKingPawnDistance = 0;
@@ -260,7 +261,7 @@ Score Entry::do_king_safety(const Position& pos, Square ksq) {
 }
 
 // Explicit template instantiation
-template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos);
+template Score Entry::do_king_safety<BLACK>(const Position& pos);
 
 } // namespace Pawns

src/pawns.h

@@ -50,13 +50,13 @@ struct Entry {
   }
 
   template<Color Us>
-  Score king_safety(const Position& pos, Square ksq) {
-    return  kingSquares[Us] == ksq && castlingRights[Us] == pos.can_castle(Us)
-          ? kingSafety[Us] : (kingSafety[Us] = do_king_safety<Us>(pos, ksq));
+  Score king_safety(const Position& pos) {
+    return  kingSquares[Us] == pos.square<KING>(Us) && castlingRights[Us] == pos.can_castle(Us)
+          ? kingSafety[Us] : (kingSafety[Us] = do_king_safety<Us>(pos));
   }
 
   template<Color Us>
-  Score do_king_safety(const Position& pos, Square ksq);
+  Score do_king_safety(const Position& pos);
 
   template<Color Us>
   Value evaluate_shelter(const Position& pos, Square ksq);