zram: move compact_store() to sysfs functions area

A cosmetic change.  We have a new code layout and keep zram per-device
sysfs store and show functions in one place.  Move compact_store() to that
handlers block to conform to current layout.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>