hpilo: add locking comment

	struct pci_dev *ilo_dev;

	/*

	 * open_lock      serializes ccb_cnt during open and close

	 * [ irq disabled ]

	 * -> alloc_lock  used when adding/removing/searching ccb_alloc,

	 *                which represents all ccbs open on the device

	 * --> fifo_lock  controls access to fifo queues shared with hw

	 *

	 * Locks must be taken in this order, but open_lock and alloc_lock

	 * are optional, they do not need to be held in order to take a

	 * lower level lock.

	 */

	spinlock_t open_lock;

	spinlock_t alloc_lock;

	spinlock_t fifo_lock;

	spinlock_t open_lock;

	struct cdev cdev;

};