slub: use alloc_pages_node() in alloc_slab_page()

For no apparent reason, we were open-coding alloc_pages_node() in this
function.

Link: https://lkml.kernel.org/r/20231228085748.1083901-3-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>