Revert "proc: don't allow async path resolution of /proc/thread-self components"

[ Upstream commit 2587890b ]

This reverts commit 0d4370cf.

No longer needed, as the io-wq worker threads have the right identity.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>