zram: keep comments within 80-columns limit

Several trivial fixups (that I should have spotted during review).

Link: https://lkml.kernel.org/r/20220914052033.838050-1-senozhatsky@chromium.org


Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>