Revert "Fix _Unwind_Backtrace for arm."

Reverting because there is a more complete fix available upstream (one
that can fully unwind in the presence of generic EHT entries).

This reverts commit 0edf7c5360403441c060618014887e9a723fe423.
Bug: 16874447
Change-Id: I5aa38183237865187156a8d8a050fd09a04ef109
1 file changed