mm: remove obsolete comments about page table lock

The callers of free_pgd_range() and hugetlb_free_pgd_range() don't hold
page table locks.  The comments seems to be obsolete, so let's remove
them.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/mm/hugetlbpage.c

@@ -633,8 +633,6 @@ static void hugetlb_free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
 
 /*
  * This function frees user-level page tables of a process.
- *
- * Must be called with pagetable lock held.
  */
 void hugetlb_free_pgd_range(struct mmu_gather *tlb,
 			    unsigned long addr, unsigned long end,

mm/memory.c

@@ -453,8 +453,6 @@ static inline void free_pud_range(struct mmu_gather *tlb, pgd_t *pgd,
 
 /*
  * This function frees user-level page tables of a process.
- *
- * Must be called with pagetable lock held.
  */
 void free_pgd_range(struct mmu_gather *tlb,
 			unsigned long addr, unsigned long end,