mm/zsmalloc: add two helpers for zs_page_migrate() and make it use zpdesc

mm/zsmalloc: add two helpers for zs_page_migrate() and make it use zpdesc

To convert page to zpdesc in zs_page_migrate(), we added
zpdesc_is_isolated()/zpdesc_zone() helpers.  No functional change.
Link: https://lkml.kernel.org/r/20241216150450.1228021-11-42.hyeyoo@gmail.com
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Alex Shi <alexs@kernel.org>
Acked-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Tested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>