This is a cleanup patch.  Change "index" to "obj_index" to keep
consistent with others in zsmalloc.

Link: http://lkml.kernel.org/r/1467882338-4300-1-git-send-email-opensource.ganesh@gmail.comSigned-off-by: NGanesh Mahendran <opensource.ganesh@gmail.com>
Reviewed-by: NSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>