Revert "Inline ldrex/strex for thumb2, remove ARMv5 remnants."

This reverts commit 62980e817c51c56208971ed5c3e98e0cb21e1685.
(cherry picked from commit 37835357ec28946652522d2bcec0968ba24c0fb6)

Change-Id: Ib4f2af8d7beee93a7ff29888cc8832b40c3cd1cb