zsmalloc: use bit_spin_lock

zsmalloc: use bit_spin_lock

Use kernel standard bit spin-lock instead of custom mess.  Even, it has
a bug which doesn't disable preemption.  The reason we don't have any
problem is that we have used it during preemption disable section by
class->lock spinlock.  So no need to go to stable.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Minchan Kim <[email protected]>
Reviewed-by: Sergey Senozhatsky <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>