Staging: rtl8192su: Build should select WIRELESS_EXT

The prevailing idiom is to select WIRELESS_EXT not depend on it.

Depending leaves this driver in a situation where it can only
be built if another driver that selects WIRELESS_EXT has been enabled.
Signed-off-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/rtl8192su/Kconfig

 config RTL8192SU
 	tristate "RealTek RTL8192SU Wireless LAN NIC driver"
 	depends on PCI && WLAN && USB
-	depends on WIRELESS_EXT
+	select WIRELESS_EXT
+	select WEXT_PRIV
 	default N
 	---help---