ath9k: Fix Kconfig depends for ATH9K_DEBUGFS

Add missing DEBUG_FS dependency for ATH9K_DEBUGFS in ath9k's Kconfig.
Signed-off-by: Dominik D. Geyer <dominik.geyer@gmx.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/Kconfig

@@ -25,7 +25,7 @@ config ATH9K
 
 config ATH9K_DEBUGFS
 	bool "Atheros ath9k debugging"
-	depends on ATH9K
+	depends on ATH9K && DEBUG_FS
 	---help---
 	  Say Y, if you need access to ath9k's statistics for
 	  interrupts, rate control, etc.