[foreign-memaccess+abi] RFR: Fix regression

[Per Minborg]

This PR fixes a regression that appeared when `MemoryAddress` was removed.

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Commit messages:
 - Fix regression

Changes: https://git.openjdk.org/panama-foreign/pull/707/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=707&range=00
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/707.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/707/head:pull/707

PR: https://git.openjdk.org/panama-foreign/pull/707