[foreign-memaccess+abi] RFR: 8258238: Some jextract samples crash with: "updating map that does not need updating"

[Jorn Vernee]

This fixes the failing assert by checking if the register map needs to be updated.

This gets the jextract samples working again, but some followup is still need to add a test case that can catch this problem.

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Commit messages:
 - Check update_map before updating the register map in sender_for_entry_frame

Changes: https://git.openjdk.java.net/panama-foreign/pull/417/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=417&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258238
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/417.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/417/head:pull/417

PR: https://git.openjdk.java.net/panama-foreign/pull/417