slab: introduce kmalloc_array()

commit a8203725dfded5c1f79dca3368a4a273e24b59bb upstream.

Introduce a kmalloc_array() wrapper that performs integer overflow
checking without zeroing the memory.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>