iwlwifi: suppress unused variable warning when compiling w/o IWLWIFI_DEBUG

This patch adds __maybe_unused attribute to priv variables used in
functions that used it solely for debug printouts

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Cc: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl3945-base.c b/drivers/net/wireless/iwlwifi/iwl3945-base.c
index 6a2c8a3..72ff20e 100644
--- a/drivers/net/wireless/iwlwifi/iwl3945-base.c
+++ b/drivers/net/wireless/iwlwifi/iwl3945-base.c
@@ -5270,8 +5270,8 @@
 			     struct device_attribute *attr,
 			     const char *buf, size_t count)
 {
+	struct iwl_priv *priv __maybe_unused = dev_get_drvdata(d);
 	int ant;
-	struct iwl_priv *priv = dev_get_drvdata(d);
 
 	if (count == 0)
 		return 0;