mm: fix typos in comments when calling __SetPageUptodate()

There are several places emphasise the effect of __SetPageUptodate(),
while the comment seems to have a typo in two places.

Link: http://lkml.kernel.org/r/20190926023705.7226-1-richardw.yang@linux.intel.com
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/userfaultfd.c

@@ -90,7 +90,7 @@ static int mcopy_atomic_pte(struct mm_struct *dst_mm,
 
 	/*
 	 * The memory barrier inside __SetPageUptodate makes sure that
-	 * preceeding stores to the page contents become visible before
+	 * preceding stores to the page contents become visible before
 	 * the set_pte_at() write.
 	 */
 	__SetPageUptodate(page);