If we hit an earlier error path in io_uring_create(), then we will have
accounted memory, but not set ctx->{sq,cq}_entries yet. Then when the
ring is torn down in error, we use those values to unaccount the memory.

Ensure we set the ctx entries before we're able to hit a potential error
path.

Cc: stable@vger.kernel.org
Reported-by: NTomáš Chaloupka <chalucha@gmail.com>
Tested-by: NTomáš Chaloupka <chalucha@gmail.com>
Reviewed-by: NStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>