[foreign-memaccess] RFR: 8248237: VarHandleByteArrayView nioAccess field should be static final

[Paul Sandoz]

Make static field final and change the name to conform to the naming convention.

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Commit messages:
 - 8248237: VarHandleByteArrayView nioAccess field should be static final

Changes: https://git.openjdk.java.net/panama-foreign/pull/214/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/214/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8248237
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/214.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/214/head:pull/214

PR: https://git.openjdk.java.net/panama-foreign/pull/214