docs: vm/page_owner: use literal blocks for param description

Sphinx generates hard-to-read lists of parameters at the bottom of the
page.  Fix them by putting literal-block markers of "::" in front of
them.

Link: https://lkml.kernel.org/r/cfd3bcc0-b51d-0c68-c065-ca1c4c202447@gmail.com
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Fixes: 57f2b54a

 ("Documentation/vm/page_owner.rst: update the documentation")
Cc: Shenghong Han <hanshenghong2019@email.szu.edu.cn>
Cc: Haowen Bai <baihaowen@meizu.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Alex Shi <seakeel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>