sq_ring_needs_enter: check whether there are sqes when SQPOLL is not enabled
sq_ring_needs_enter: check whether there are sqes when SQPOLL is not enabled

Indeed I'm not sure this patch is necessary, robust applications
should not call io_uring_submit when there are not sqes to submmit.
But still try to add this check, I have seen some applications which
call io_uring_submit(), but there are not sqes to submit.

Signed-off-by: Xiaoguang Wang <ec1c4725ddf7c229d2c524e12c387dddb1073659@linux.alibaba.com>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing