iwlagn: Add power_level module parameter

Add power_level module parameter to set the default power save level.
Power save level has range from 1 - 5, default power save level is 1.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index b719628..77ceb8d 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -3831,6 +3831,11 @@
 MODULE_PARM_DESC(power_save,
 		 "enable WiFi power management (default: disable)");
 
+module_param_named(power_level, iwlagn_mod_params.power_level,
+		int, S_IRUGO);
+MODULE_PARM_DESC(power_level,
+		 "default power save level (range from 1 - 5, default: 1)");
+
 /*
  * For now, keep using power level 1 instead of automatically
  * adjusting ...