fs/io_uring: Prioritise checking faster conditions first in io_write

This commit reorders the conditions in a branch in io_write. The
reorder to check 'ret2 == -EAGAIN' first as checking
'(req->ctx->flags & IORING_SETUP_IOPOLL)' will likely be more
expensive due to 2x memory derefences.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Link: https://lore.kernel.org/r/20211017013229.4124279-1-goldstein.w.n@gmail.com


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