[POWERPC] Fix non HUGETLB_PAGE build warning

arch/powerpc/mm/mmu_context_64.c: In function 'init_new_context':
arch/powerpc/mm/mmu_context_64.c:31: warning: unused variable 'new_context'

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index d5fd390..319826e 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -551,6 +551,7 @@
  *
  * This is also called in init_new_context() to change back the user
  * psize from whatever the parent context had it set to
+ * N.B. This may be called before mm->context.id has been set.
  *
  * This function will only change the content of the {low,high)_slice_psize
  * masks, it will not flush SLBs as this shall be handled lazily by the