zram: drop not used table `count' member

(cherry pick from commit 59fc86a4922f1a1c0f69eac758a7e2b2b138aab4)

struct table `count' member is not used.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Bug: 24810447
Change-Id: Ifeadc3ea1e72ba83fba5fc0b0753d461e8b8b84c