powerpc: Fix hugetlb with CONFIG_PPC_MM_SLICES=y

Commit 41151e77 ("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>

arch/powerpc/mm/hugetlbpage-book3e.c

@@ -52,7 +52,7 @@ void book3e_hugetlb_preload(struct mm_struct *mm, unsigned long ea, pte_t pte)
 	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;

arch/powerpc/mm/hugetlbpage.c

@@ -690,7 +690,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 					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 hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 
 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);