powerpc/mm: Fix compile warning

arch/powerpc/mm/tlb_nohash.c: In function 'flush_tlb_mm':
arch/powerpc/mm/tlb_nohash.c:128: warning: unused variable 'cpu_mask'

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/mm/tlb_nohash.c

@@ -125,7 +125,6 @@ static void do_flush_tlb_page_ipi(void *param)
 
 void flush_tlb_mm(struct mm_struct *mm)
 {
-	cpumask_t cpu_mask;
 	unsigned int pid;
 
 	preempt_disable();