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.