ITER_XARRAY: don't open-code DIV_ROUND_UP()

Reviewed-by: NJeff Layton <jlayton@kernel.org>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

lib/iov_iter.c

@@ -1386,15 +1386,7 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i,
 	offset = pos & ~PAGE_MASK;
 	*_start_offset = offset;
 
-	count = 1;
-	if (size > PAGE_SIZE - offset) {
-		size -= PAGE_SIZE - offset;
-		count += size >> PAGE_SHIFT;
-		size &= ~PAGE_MASK;
-		if (size)
-			count++;
-	}
-
+	count = DIV_ROUND_UP(size + offset, PAGE_SIZE);
 	if (count > maxpages)
 		count = maxpages;