UPSTREAM: io_uring: support MSG_WAITALL for IORING_OP_SEND(MSG)

commit 4c3c0943 upstream.

Like commit 7ba89d2a for recv/recvmsg, support MSG_WAITALL for the
send side. If this flag is set and we do a short send, retry for a
stream of seqpacket socket.

Change-Id: I86b7a362c9d5e91c9a663635feade329c9d9e4fe
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit 3c1a3d02)
Bug: 268174392
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>