iwlwifi: re-introduce per device debugging

Commit "iwlwifi: make debug level more user friendly" cleaned up the
debug level handling. In doing so it created a single global debug
level for all devices. Some setups do consits of more that one iwlwifi
device and in these setups there is a requirement that debug levels
should be unique per device.

We now re-introduce the per device debugging while maintaining the
cleanup effort of the previous patch.

The maintain the global debug level and now introduce a per-device debug
level that will be used if it (the per-device debug level) is set. The
per-device debug level can be controlled via the debug_level sysfs file
while the global debug level is controlled by the debug module parameter.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-4965.c b/drivers/net/wireless/iwlwifi/iwl-4965.c
index 6702148..62436a9 100644
--- a/drivers/net/wireless/iwlwifi/iwl-4965.c
+++ b/drivers/net/wireless/iwlwifi/iwl-4965.c
@@ -46,7 +46,7 @@
 #include "iwl-sta.h"
 
 static int iwl4965_send_tx_power(struct iwl_priv *priv);
-static int iwl4965_hw_get_temperature(const struct iwl_priv *priv);
+static int iwl4965_hw_get_temperature(struct iwl_priv *priv);
 
 /* Highest firmware API version supported */
 #define IWL4965_UCODE_API_MAX 2
@@ -1680,7 +1680,7 @@
  *
  * A return of <0 indicates bogus data in the statistics
  */
-static int iwl4965_hw_get_temperature(const struct iwl_priv *priv)
+static int iwl4965_hw_get_temperature(struct iwl_priv *priv)
 {
 	s32 temperature;
 	s32 vt;