zram: use copy_page for full page copy

Some architectures, such as arm, have implemented optimized copy_page for
full page copying.

Replace the full page memcpy with copy_page to take advantage of the
optimization.

Link: https://lkml.kernel.org/r/20231007070554.8657-1-mark-pk.tsai@mediatek.com


Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: YJ Chiang <yj.chiang@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>