uClibc: Backport uClibc master git commit...

uClibc: Backport uClibc master git commit fd355bc1dbcb794ae1abf0fad1459e28d8567ba0 (eventfd.h: Use new "bits/" scheme for arch-specific flags)

This patch adds missing architecture-specific headers for use with
eventfd(2). Fixes #16679.

Signed-off-by: Luis Dallos <ld@nkvd.ignorelist.com>

SVN-Revision: 42916