[foreign-memaccess] RFR: 8246052: MemorySegment::mapFromPath should take an offset

[Maurizio Cimadamore]

This is a trivial followup - one of the benchmark working with mapped segments was not upgraded to take the extra
argument.

-------------

Commit messages:
 - Fix test

Changes: https://git.openjdk.java.net/panama-foreign/pull/189/files
 Webrev: https://webrevs.openjdk.java.net/panama-foreign/189/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8246052
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/189.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/189/head:pull/189

PR: https://git.openjdk.java.net/panama-foreign/pull/189