powerhint: add tapered_dvfs_headroom_enabled node

Test: Load powerhint on device and boot

Bug: 294612493
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:1337a00fbedfb4db09bf7e549c4820265bed1298)
Merged-In: I823a18d5ee7b072115442a9af19645cce0605d72
Change-Id: I823a18d5ee7b072115442a9af19645cce0605d72
3 files changed