cpumask: statement expressions confuse some versions of gcc

when you take the address of the result. Noticed on a sparc64 compile
using a version 3.4.5 cross compiler.

kernel/time/tick-common.c: In function `tick_check_new_device':
kernel/time/tick-common.c:210: error: invalid lvalue in unary `&'
...

Just make it a regular expression.

Signed-off-by: Stephen Rothwell <[e-mail]>
Acked-by: Ingo Molnar <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/cpumask.h

···
  * gcc optimizes it out (it's a constant) and there's no huge stack
  * variable created:
  */
-#define cpumask_of_cpu(cpu) ({ *get_cpu_mask(cpu); })
+#define cpumask_of_cpu(cpu) (*get_cpu_mask(cpu))
 
 
 #define CPU_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(NR_CPUS)