page_pool: update document about fragment API

page_pool: update document about fragment API

As more drivers begin to use the fragment API, update the
document about how to decide which API to use for the
driver author.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
CC: Lorenzo Bianconi <lorenzo@kernel.org>
CC: Alexander Duyck <alexander.duyck@gmail.com>
CC: Liang Chen <liangchen.linux@gmail.com>
CC: Alexander Lobakin <aleksander.lobakin@intel.com>
CC: Dima Tisnek <dimaqq@gmail.com>
Link: https://lore.kernel.org/r/20231020095952.11055-5-linyunsheng@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit 8ab32fa1c7947f4807b1d98af2d411a2587bb841)
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Change-Id: I03e5460b08e7607bd85a44b37930d770a0c56c9d