remove zero-size array in io_uring.h
remove zero-size array in io_uring.h

This fixes compilation with -Werror=pedantic.

Signed-off-by: Akinobu Mita <3807cf899f217da549814bf6c330d3b6e6819ccf@gmail.com>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@kernel.dk>

axboe/liburing,axboe/liburing,axboe/liburing