Include cpu-features.h.

Needed for code that tests for _ARM_HAVE_LDREX_STREX.

Change-Id: I3504eeda935a444900236722e8de70b58b8bd8d1
Merge (-sours) commit '9b67cc0ba439bf17c247123c657b9e73181149b6' into oxygen_4.3

* commit '9b67cc0ba439bf17c247123c657b9e73181149b6':
  Include cpu-features.h.