[foreign-abi] RFR: 8248487: Add static helpers to access segments (continued)

[Maurizio Cimadamore]

Fix bad references to static accessors as per recent renaming

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Commit messages:
 - Fix bad references to static accessors

Changes: https://git.openjdk.java.net/panama-foreign/pull/234/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/234/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8248487
  Stats: 16 lines in 3 files changed: 0 ins; 0 del; 16 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/234.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/234/head:pull/234

PR: https://git.openjdk.java.net/panama-foreign/pull/234