Revert "tracing: Use .flush() call to wake up readers"

This reverts commit 898127d6 which is
commit e5d7c191 upstream.

It breaks the Android kernel build and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I59ae44963d713c3f116d8a6d02dfa36dda183e44
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>