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>
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index d67db4b..90bb6d9 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -633,8 +633,6 @@
 
 /*
  * 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,
diff --git a/mm/memory.c b/mm/memory.c
index 1f2287e..15744b2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -453,8 +453,6 @@
 
 /*
  * 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,