p54: only unregister ieee80211_hw when it has been registered

p54_unregister_common may now be called by the backend
driver's remove routine, even if the ieee80211_hw device
struct was never successfully registered.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/p54/p54.h

@@ -173,6 +173,7 @@ struct p54_common {
 	struct sk_buff_head tx_pending;
 	struct sk_buff_head tx_queue;
 	struct mutex conf_mutex;
+	bool registered;
 
 	/* memory management (as seen by the firmware) */
 	u32 rx_start;