Staging: asus_oled: fix build dependancy

asus_oled depends on the CONFIG_USB_SUPPORT, I have only build tested
the patch.
Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/asus_oled/Kconfig

 config ASUS_OLED
 	tristate "Asus OLED driver"
+	depends on USB
 	default N
 	---help---
 	  Enable support for the OLED display present in some Asus laptops.