mm/zsmalloc: convert SetZsPageMovable and remove unused funcs

mm/zsmalloc: convert SetZsPageMovable and remove unused funcs

Convert SetZsPageMovable() to use zpdesc, and then remove unused funcs:
get_next_page()/get_first_page()/is_first_page().

Link: https://lkml.kernel.org/r/20241216150450.1228021-17-42.hyeyoo@gmail.com
Originally-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Alex Shi <alexs@kernel.org>
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
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>