[vectorIntrinsics] RFR: 8264882: Build failure without C2 on x86_32/aarch64/ppc/s390/arm

[Jie Fu]

Hi all,

Build failure was observed on x86_32 if C2 is disabled.

The reason is that `assert(!Matcher::supports_vector_calling_convention(), "not implemented")` requires `Matcher` which is C2's code.
And the same bug should also exist for aarch64/ppc/s390/arm in theory.

This assert is useless and can be removed safely since there is `Unimplemented();` after it.

Let's fix it.

Thanks.
Best regards,
Jie

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Commit messages:
 - 8264882: Build failure without C2 on x86_32/aarch64/ppc/s390/arm

Changes: https://git.openjdk.java.net/panama-vector/pull/63/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=63&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264882
  Stats: 5 lines in 5 files changed: 0 ins; 5 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/63.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/63/head:pull/63

PR: https://git.openjdk.java.net/panama-vector/pull/63