[IA64] Update comment that references __get_cpu_var

__get_cpu_var was removed. Update the comments.

Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/include/asm/percpu.h

@@ -35,8 +35,8 @@ extern void *per_cpu_init(void);
 
 /*
  * Be extremely careful when taking the address of this variable!  Due to virtual
- * remapping, it is different from the canonical address returned by __get_cpu_var(var)!
- * On the positive side, using __ia64_per_cpu_var() instead of __get_cpu_var() is slightly
+ * remapping, it is different from the canonical address returned by this_cpu_ptr(&var)!
+ * On the positive side, using __ia64_per_cpu_var() instead of this_cpu_ptr() is slightly
  * more efficient.
  */
 #define __ia64_per_cpu_var(var) (*({					\