thp: update split_huge_page_pmd() comment

According to 78ddc53 ("thp: rename split_huge_page_pmd() to
split_huge_pmd()"), update related comment.

Link: http://lkml.kernel.org/r/20190731033406.185285-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Kefeng Wang

arch/powerpc/mm/book3s64/hash_utils.c

@@ -1748,7 +1748,7 @@ void flush_hash_hugepage(unsigned long vsid, unsigned long addr,
 	/*
 	 * IF we try to do a HUGE PTE update after a withdraw is done.
 	 * we will find the below NULL. This happens when we do
-	 * split_huge_page_pmd
+	 * split_huge_pmd
 	 */
 	if (!hpte_slot_array)
 		return;

include/asm-generic/pgtable.h

@@ -1002,9 +1002,8 @@ static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
  * need this). If THP is not enabled, the pmd can't go away under the
  * code even if MADV_DONTNEED runs, but if THP is enabled we need to
  * run a pmd_trans_unstable before walking the ptes after
- * split_huge_page_pmd returns (because it may have run when the pmd
- * become null, but then a page fault can map in a THP and not a
- * regular page).
+ * split_huge_pmd returns (because it may have run when the pmd become
+ * null, but then a page fault can map in a THP and not a regular page).
  */
 static inline int pmd_trans_unstable(pmd_t *pmd)
 {