slab: silence sparse warning with type-based partitioning

slab: silence sparse warning with type-based partitioning

Sparse does not know __builtin_infer_alloc_token() and complains:

	sparse: sparse: undefined identifier '__builtin_infer_alloc_token'

Fix it by using a dummy variant of __kmalloc_token() if __CHECKER__ is
defined.

Fixes: feb662d9168b ("slab: support for compiler-assisted type-based slab cache partitioning")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202607110912.nZTqfCrH-lkp@intel.com/
Signed-off-by: Marco Elver <elver@google.com>
Link: https://patch.msgid.link/20260721092005.1986693-1-elver@google.com
Acked-by: Harry Yoo (Oracle) <harry@kernel.org>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>