mac80211: refactor debugfs function generation code

refactor mac80211 debugfs code by using a format&copy function, instead of
duplicating the code for each generated function.

this change reduces about 600B from mac80211.ko

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/debugfs.h b/net/mac80211/debugfs.h
index 09cc9be..7c87529 100644
--- a/net/mac80211/debugfs.h
+++ b/net/mac80211/debugfs.h
@@ -4,6 +4,8 @@
 #ifdef CONFIG_MAC80211_DEBUGFS
 extern void debugfs_hw_add(struct ieee80211_local *local);
 extern int mac80211_open_file_generic(struct inode *inode, struct file *file);
+extern int mac80211_format_buffer(char __user *userbuf, size_t count,
+				  loff_t *ppos, char *fmt, ...);
 #else
 static inline void debugfs_hw_add(struct ieee80211_local *local)
 {