Revert "pipe: avoid unnecessary EPOLLET wakeups under normal loads"

This reverts commit e91da23c which is
commit 3b844826 upstream.

It is a nice pipe benchmark improvement, but not really needed for the
android trees, especially as it breaks the abi, so revert it.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ie785d08c9f6bea569c9cf5623736fa303bff56b1