[foreign-memaccess] Integrated: 8252866: MemoryAccess.setAddress should take Addressable, not MemoryAddress (follow up)

[Maurizio Cimadamore]

This small patch fixes an oversight - MemoryAccess.setAddressAtOffset should call address() on the incoming value,
before dispatching on the var handle.

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Commit messages:
 - Fix issue in MemoryAccess.setAddressAtOffset

Changes: https://git.openjdk.java.net/panama-foreign/pull/315/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=315&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252866
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/315.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/315/head:pull/315

PR: https://git.openjdk.java.net/panama-foreign/pull/315