fs/pipe: set FMODE_NOWAIT in create_pipe_files()

Rather than have the caller set the FMODE_NOWAIT flags for both output
files, move it to create_pipe_files() where other f_mode flags are set
anyway with stream_open(). With that, both __do_pipe_flags() and
io_pipe() can remove the manual setting of the NOWAIT flags.

No intended functional changes, just a code cleanup.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/1f0473f8-69f3-4eb1-aa77-3334c6a71d24@kernel.dk


Signed-off-by: Christian Brauner <brauner@kernel.org>