vndk-def: Add --revert flag to deps-closure

This commit adds --revert flag to deps-closure so that a user can list
the transitive users of a library.

Bug: 62644173
Test: ./vndk_definition_tool.py deps-closure --revert /system/lib/libc.so ...
Change-Id: I03aab8d629c88074d6111659853b1396d87326ad