Staging: wlan-ng: use WIRELESS_EXT, not CONFIG_WIRELESS_EXT

Kconfig doesn't work with variables starting with CONFIG_
Signed-off-by: NSolomon Peachy <pizza@shaftnet.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/wlan-ng/Kconfig

 config PRISM2_USB
 	tristate "Prism2.5/3 USB driver"
-	depends on WLAN_80211 && USB && CONFIG_WIRELESS_EXT
+	depends on WLAN_80211 && USB && WIRELESS_EXT
 	default n
 	---help---
 	  This is the wlan-ng prism 2.5/3 USB driver for a wide range of