sh: maple: Do not pass SLAB_POISON to kmem_cache_create()

SLAB_POISON is not a valid flag for kmem_create_cache() unless
CONFIG_DEBUG_SLAB is set, so remove it from the flags argument.

Acked-by: Adrian McMenamin <adrian@newgolddream.dyndns.info>
Signed-off-by: Matt Fleming <mjf@gentoo.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>