io_uring: drop exec checks from io_req_task_submit

io_uring: drop exec checks from io_req_task_submit

In case of on-exec io_uring cancellations, tasks already wait for all
submitted requests to get completed/cancelled, so we don't need to check
for ->in_execve separately.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/be8707049f10df9d20ca03dc4ca3316239b5e8e0.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>