doc: linux-wpan: Change the old function names to the lastest function names

The function declaration in the lastest include/net/mac802154.h has been
changed since v3.19.

ieee802154_alloc_device => ieee802154_alloc_hw
ieee802154_free_device => ieee802154_free_hw
ieee802154_register_device => ieee802154_register_hw
ieee802154_unregister_device => ieee802154_unregister_hw

However, the description in the Device drivers API section of
Documentation/networking/ieee802154.txt is still in the state of
v3.18.63.

Signed-off-by: Jian-Hong Pan <starnight@g.ncu.edu.tw>
Acked-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/networking/ieee802154.txt

@@ -84,17 +84,17 @@ Device drivers API
 ==================
 
 The include/net/mac802154.h defines following functions:
- - struct ieee802154_dev *ieee802154_alloc_device
-   (size_t priv_size, struct ieee802154_ops *ops):
-   allocation of IEEE 802.15.4 compatible device
+ - struct ieee802154_hw *
+   ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops):
+   allocation of IEEE 802.15.4 compatible hardware device
 
- - void ieee802154_free_device(struct ieee802154_dev *dev):
-   freeing allocated device
+ - void ieee802154_free_hw(struct ieee802154_hw *hw):
+   freeing allocated hardware device
 
- - int ieee802154_register_device(struct ieee802154_dev *dev):
-   register PHY in the system
+ - int ieee802154_register_hw(struct ieee802154_hw *hw):
+   register PHY which is the allocated hardware device, in the system
 
- - void ieee802154_unregister_device(struct ieee802154_dev *dev):
+ - void ieee802154_unregister_hw(struct ieee802154_hw *hw):
    freeing registered PHY
 
 Moreover IEEE 802.15.4 device operations structure should be filled.