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.c b/arch/powerpc/mm/hugetlbpage.c
index 3a5f59d..48b65be 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -690,7 +690,7 @@
 					unsigned long len, unsigned long pgoff,
 					unsigned long flags)
 {
-#ifdef CONFIG_MM_SLICES
+#ifdef CONFIG_PPC_MM_SLICES
 	struct hstate *hstate = hstate_file(file);
 	int mmu_psize = shift_to_mmu_psize(huge_page_shift(hstate));
 
@@ -702,7 +702,7 @@
 
 unsigned long vma_mmu_pagesize(struct vm_area_struct *vma)
 {
-#ifdef CONFIG_MM_SLICES
+#ifdef CONFIG_PPC_MM_SLICES
 	unsigned int psize = get_slice_psize(vma->vm_mm, vma->vm_start);
 
 	return 1UL << mmu_psize_to_shift(psize);