Upgrade libtracefs to libtracefs-1.6.4

This project was upgraded with external_updater.
Usage: tools/external_updater/updater.sh update libtracefs
For more info, check https://cs.android.com/android/platform/superproject/+/master:tools/external_updater/README.md

Test: TreeHugger
Change-Id: I8fee49cf351dad60da6543b4eaa4cffea01a7fc2