arch/powerpc/mm/pgtable.c: another missed conversion

Fixes: e05c7b1f ("mm: pgtable: add shortcuts for accessing kernel PMD and PTE")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/mm/pgtable.c

@@ -264,7 +264,7 @@ int huge_ptep_set_access_flags(struct vm_area_struct *vma,
 #if defined(CONFIG_PPC_8xx)
 void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte)
 {
-	pmd_t *pmd = pmd_ptr(mm, addr);
+	pmd_t *pmd = pmd_off(mm, addr);
 	pte_basic_t val;
 	pte_basic_t *entry = &ptep->pte;
 	int num = is_hugepd(*((hugepd_t *)pmd)) ? 1 : SZ_512K / SZ_4K;