xen: Use this_cpu_ops

Use this_cpu_ops to reduce code size and simplify things in various places.

V3->V4:
	Move instance of this_cpu_inc_return to a later patchset so that
	this patch can be applied without infrastructure changes.

Cc: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/arch/x86/xen/multicalls.h b/arch/x86/xen/multicalls.h
index 9e565da..4ec8035 100644
--- a/arch/x86/xen/multicalls.h
+++ b/arch/x86/xen/multicalls.h
@@ -22,7 +22,7 @@
 	unsigned long flags;
 	/* need to disable interrupts until this entry is complete */
 	local_irq_save(flags);
-	__get_cpu_var(xen_mc_irq_flags) = flags;
+	__this_cpu_write(xen_mc_irq_flags, flags);
 }
 
 static inline struct multicall_space xen_mc_entry(size_t args)