mm/slub: remove the check of !kmem_cache_has_cpu_partial()

The check of !kmem_cache_has_cpu_partial(s) with
CONFIG_SLUB_CPU_PARTIAL enabled here is always false.

We have already checked kmem_cache_debug() earlier and if it was true,
then we either continued or broke from the loop so we can't reach this
code in that case and don't need to check kmem_cache_debug() as part of
kmem_cache_has_cpu_partial() again. Here we can remove it.

Signed-off-by: Xiongwei Song <xiongwei.song@windriver.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>