Complete the setup for a character device's state structure
#include <qvm/cdev.h>
int cdev_setup(struct cdev_state *cds, struct vdev_s *vdev, unsigned size)
This function allocates both the input and output buffers; and makes them both the size you specify in size. If you want to provide your own input and output buffers, set size to 0 (zero).
EOK on success; otherwise an errno value.