RFR: 8346157: [s390x/Ubsan]: runtime error: pointer index expression with base 0x000000001000 overflowed to 0xfffffffffffffff0

[Amit Kumar]

Fixes ubsan warning in mallocTracker.cpp

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Commit messages:
 - updates data type from uint8_t to uintptr_t to make ubsan happy

Changes: https://git.openjdk.org/jdk/pull/22885/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22885&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346157
  Stats: 8 lines in 1 file changed: 3 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/22885.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22885/head:pull/22885

PR: https://git.openjdk.org/jdk/pull/22885