powerpc: Fix hugetlb with CONFIG_PPC_MM_SLICES=y

Commit 41151e77a4 ("powerpc: Hugetlb for BookE") added some
#ifdef CONFIG_MM_SLICES conditionals to hugetlb_get_unmapped_area()
and vma_mmu_pagesize().  Unfortunately this is not the correct config
symbol; it should be CONFIG_PPC_MM_SLICES.  The result is that
attempting to use hugetlbfs on 64-bit Power server processors results
in an infinite stack recursion between get_unmapped_area() and
hugetlb_get_unmapped_area().

This fixes it by changing the #ifdef to use CONFIG_PPC_MM_SLICES
in those functions and also in book3e_hugetlb_preload().

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/mm/hugetlbpage-book3e.c b/arch/powerpc/mm/hugetlbpage-book3e.c
index 1295b7c..343ad0b 100644
--- a/arch/powerpc/mm/hugetlbpage-book3e.c
+++ b/arch/powerpc/mm/hugetlbpage-book3e.c
@@ -52,7 +52,7 @@
 	if (unlikely(is_kernel_addr(ea)))
 		return;
 
-#ifdef CONFIG_MM_SLICES
+#ifdef CONFIG_PPC_MM_SLICES
 	psize = mmu_get_tsize(get_slice_psize(mm, ea));
 	tsize = mmu_get_psize(psize);
 	shift = mmu_psize_defs[psize].shift;