x86/apic: Add replacement for cpu_mask_to_apicid()

As preparation for replacing the vector allocator, provide a new function
which takes a cpu number instead of a cpu mask to calculate/lookup the
resulting APIC destination id.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Yu Chen <yu.c.chen@intel.com>
Acked-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rui Zhang <rui.zhang@intel.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Len Brown <lenb@kernel.org>

arch/x86/xen/apic.c

@@ -178,6 +178,7 @@ static struct apic xen_pv_apic = {
 	.set_apic_id 			= xen_set_apic_id, /* Can be NULL on 32-bit. */
 
 	.cpu_mask_to_apicid		= flat_cpu_mask_to_apicid,
+	.calc_dest_apicid		= apic_flat_calc_apicid,
 
 #ifdef CONFIG_SMP
 	.send_IPI_mask 			= xen_send_IPI_mask,