slub: make ->cpu_partial unsigned

slub: make ->cpu_partial unsigned

	/*
	 * cpu_partial determined the maximum number of objects
	 * kept in the per cpu partial lists of a processor.
	 */

Can't be negative.

Orabug: 28620592

We can't reproduce the issue, this patch is expected to help in theory.

Link: http://lkml.kernel.org/r/20180305200730.15812-15-adobriyan@gmail.com
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Reviewed-by: John Sobecki <john.sobecki@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>