Don't touch iter->iov and iov in between __io_import_iovec() and
io_req_map_rw(), the former function aleady sets it correctly, because it
creates one more case with NULL'ed iov to consider in io_req_map_rw().
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>