usb/misc: fix chaoskey build, needs HW_RANDOM

Fix build errors when HW_RANDOM is not enabled:

drivers/built-in.o: In function `chaoskey_disconnect':
chaoskey.c:(.text+0x5f3f00): undefined reference to `hwrng_unregister'
drivers/built-in.o: In function `chaoskey_probe':
chaoskey.c:(.text+0x5f42a6): undefined reference to `hwrng_register'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/Kconfig

@@ -258,6 +258,7 @@ config USB_LINK_LAYER_TEST
 
 config USB_CHAOSKEY
 	tristate "ChaosKey random number generator driver support"
+	depends on HW_RANDOM
 	help
 	  Say Y here if you want to connect an AltusMetrum ChaosKey to
 	  your computer's USB port. The ChaosKey is a hardware random