iwmc3200wifi: add a mutex to protect iwm_reset_worker

The patch adds a mutex to protect the iwm_reset_worker against netdev
ndo_open and ndo_stop because all of them call iwm_up and iwm_down in
the implementation. Note the latter two are already protected by
rtnl. So if iwm_reset_worker is not required in the future, the mutex
can also be removed.

Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: Samuel Ortiz <samuel.ortiz@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwmc3200wifi/iwm.h b/drivers/net/wireless/iwmc3200wifi/iwm.h
index 4aa0ad1..77c339f 100644
--- a/drivers/net/wireless/iwmc3200wifi/iwm.h
+++ b/drivers/net/wireless/iwmc3200wifi/iwm.h
@@ -288,6 +288,7 @@
 	u8 *eeprom;
 	struct timer_list watchdog;
 	struct work_struct reset_worker;
+	struct mutex mutex;
 	struct rfkill *rfkill;
 
 	char private[0] __attribute__((__aligned__(NETDEV_ALIGN)));