stdlib: atexit: include <sys/cdefs.h>

Change-Id: Ib9eb167710a021e0a2b5c77a06a9338cdc748e6d
Fix mako builds. Do not merge.

Revert "Regenerate msm_ion.h."

This reverts commit 3fac8f7f492302ae680288996e31debc645fd684.