[vectorIntrinsics] RFR: Fix compilation error in perf reduction tests

[Paul Sandoz]

The recent merge, bringing in updates to testing of reduction operations, resulted in a compilation error for the perf tests, which results in build failures.

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Commit messages:
 - Fix compilation error in perf reduction tests

Changes: https://git.openjdk.java.net/panama-vector/pull/177/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=177&range=00
  Stats: 2200 lines in 37 files changed: 156 ins; 1684 del; 360 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/177.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/177/head:pull/177

PR: https://git.openjdk.java.net/panama-vector/pull/177