xen: XEN_ACPI_PROCESSOR is Dom0-only

Add a respective dependency.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

drivers/xen/Kconfig

@@ -269,7 +269,7 @@ config XEN_ACPI_HOTPLUG_CPU
 
 config XEN_ACPI_PROCESSOR
 	tristate "Xen ACPI processor"
-	depends on XEN && X86 && ACPI_PROCESSOR && CPU_FREQ
+	depends on XEN && XEN_DOM0 && X86 && ACPI_PROCESSOR && CPU_FREQ
 	default m
 	help
           This ACPI processor uploads Power Management information to the Xen