mm/zsmalloc: get rid of PAGE_MASK

Use offset_in_page() macro instead of 'val & ~PAGE_MASK'

Link: https://lkml.kernel.org/r/20230516095029.49036-2-avromanov@sberdevices.ru


Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>