releasetools: Skip checking files with non-monotonic ranges.

Bug: 79951743
Test: Run validate_target_files.py on target_files.zip that has
      non-monotonic ranges listed in IMAGES/system.map.
Change-Id: I28d3ca6972d361362589cd51e60731af9994a551
Merged-In: I28d3ca6972d361362589cd51e60731af9994a551
(cherry picked from commit d32936d6)