io_uring: fix wrong condition to grab uring lock

Grab uring lock when we are in io-worker rather than in the original
or system-wq context since we already hold it in these two situation.

Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Fixes: b66ceaf3 ("io_uring: move iopoll reissue into regular IO path")
Link: https://lore.kernel.org/r/20211014140400.50235-1-haoxu@linux.alibaba.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>