ART-tests: Remove DX dependency from 661-checker-simd-reduc

In a few test cases D8 generated code makes ART swap 2 similar PHI
instructions. This CL updates the check conditions for D8 and enables
it.

Test: art/test.py -r -b --host -t 661-checker-simd-reduc
Bug: 65168732
Change-Id: I0cde3ab21b33bde48da3209df206739ad9d99e89