Simplify NMP eval in qsearch
Passed non-regression STC:
https://tests.stockfishchess.org/tests/view/6834e9436ec7634154f9cd6e
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 24864 W: 6626 L: 6394 D: 11844
Ptnml(0-2): 62, 2806, 6477, 3012, 75
Passed non-regression LTC:
https://tests.stockfishchess.org/tests/view/683598fd6ec7634154f9ce82
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 200148 W: 51461 L: 51424 D: 97263
Ptnml(0-2): 92, 21672, 56503, 21721, 86
closes https://github.com/official-stockfish/Stockfish/pull/6109
Bench: 2316591