xen: move x86-specific xen_vector_callback_enabled to sys/x86

This is x86-only and so should not be in the common area.

Submitted by: Elliott Mitchell <ehem+freebsd@m5p.com>
Reviewed by: royger
Differential revision: https://reviews.freebsd.org/D29040

sys/x86/include/xen/xen-os.h

@@ -33,6 +33,9 @@
 /* Everything below this point is not included by assembler (.S) files. */
 #ifndef __ASSEMBLY__
 
+/* If non-zero, the hypervisor has been configured to use a direct vector */
+extern int xen_vector_callback_enabled;
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* _MACHINE_X86_XEN_XEN_OS_H_ */

sys/xen/xen_intr.h

@@ -38,9 +38,6 @@
 /** Registered Xen interrupt callback handle. */
 typedef void * xen_intr_handle_t;
 
-/** If non-zero, the hypervisor has been configured to use a direct vector */
-extern int xen_vector_callback_enabled;
-
 void xen_intr_handle_upcall(struct trapframe *trap_frame);
 
 /**