Remove 'si' StateInfo variable/parameter.
Since st is a member of position we don't need to pass it separately as
parameter.
While being there also remove some line in pos_is_ok, where
a copy of StateInfo was made by using default copy constructor and
then verified it's correctedness by doing a memcmp.
There is no point in doing that.
Passed non-regression test
https://tests.stockfishchess.org/tests/view/
64098d562644b62c33942b35
LLR: 3.24 (-2.94,2.94) <-1.75,0.25>
Total: 548960 W: 145834 L: 146134 D: 256992
Ptnml(0-2): 1617, 57652, 156261, 57314, 1636
closes https://github.com/official-stockfish/Stockfish/pull/4444
No functional change
projects / stockfish / commit