xen/xenbus: making backend support modular is too complex

Impact: build fix

Making the xenbus backend support a separate module is needlessly complex
and causes build failures.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/Kconfig

@@ -30,7 +30,7 @@ config XEN_DEV_EVTCHN
 	  If in doubt, say yes.
 
 config XEN_BACKEND
-	tristate "Backend driver support"
+	bool "Backend driver support"
 	depends on XEN_DOM0
 	default y
 	help