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 <sfr@canb.auug.org.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>