io_uring: consolidate fio_ioring{,_cmd}_queue_init()

fio_ioring_cmd_queue_init() is identical to fio_ioring_queue_init()
except for the additional IORING_SETUP_SQE128 and IORING_SETUP_CQE32
flags. Check for is_uring_cmd_eng in fio_ioring_queue_init() and set
these flags accordingly. Replace fio_ioring_cmd_queue_init() with
fio_ioring_queue_init().

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>