iwlagn: remove forgotten debugfs function

It seems that due to merge issues between different
trees or so this function prototype wasn't removed
when it should have been, do it now.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>

drivers/net/wireless/iwlwifi/iwl-debug.h

@@ -78,8 +78,6 @@ static inline void iwl_print_hex_dump(struct iwl_priv *priv, int level,
 #ifdef CONFIG_IWLWIFI_DEBUGFS
 int iwl_dbgfs_register(struct iwl_priv *priv, const char *name);
 void iwl_dbgfs_unregister(struct iwl_priv *priv);
-extern int iwl_dbgfs_statistics_flag(struct iwl_priv *priv, char *buf,
-				     int bufsz);
 #else
 static inline int iwl_dbgfs_register(struct iwl_priv *priv, const char *name)
 {