[vectorIntrinsics] RFR: Make method package private.

[Paul Sandoz]

While going more carefully through https://github.com/openjdk/jdk/pull/5873/ i noticed that the following method on `VectorMask` is public:


<F> VectorMask<F> check(Class<? extends VectorMask<F>> maskClass, Vector<F> vector);


This is primarily intended for internal use. For now i think it best to make it package private.

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Commit messages:
 - Make method package private.

Changes: https://git.openjdk.java.net/panama-vector/pull/152/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=152&range=00
  Stats: 2 lines in 2 files changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/152.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/152/head:pull/152

PR: https://git.openjdk.java.net/panama-vector/pull/152