[LV][AArch64] Fix reductions costs in strict-fadd-cost.ll. NFC

These tests were originally added in 0aff1798, where they
were measuring the cost of fadd and fmuladd reductions, which should be fairly
high cost. For some reason, due to the forced vector factors, the debug costs
of each instruction are printed twice by the vectorizer. Once as if the
instruction is a simple fadd/fmuladd, and later with the correct reduction
cost.

In d827865e the costs were updated to match the first
print statements, where they would be better to match the second to test the
cost of the reduction.

This patch returns them to testing the original reduction costs.