RFR: 8255672: Replace PhaseTransform::eqv by pointer equality check

[Tobias Hartmann]

`PhaseTransform::eqv(n1, n2)` can be replaced by `n1 == n2`. Code in adlc also refers to it but already uses `==` instead.

Thanks,
Tobias

-------------

Commit messages:
 - 8255672: Replace PhaseTransform::eqv by pointer equality check

Changes: https://git.openjdk.java.net/jdk/pull/999/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=999&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255672
  Stats: 138 lines in 10 files changed: 30 ins; 15 del; 93 mod
  Patch: https://git.openjdk.java.net/jdk/pull/999.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/999/head:pull/999

PR: https://git.openjdk.java.net/jdk/pull/999