mm/kasan: simplify and refine kasan_cache code

mm/kasan: simplify and refine kasan_cache code

struct 'kasan_cache' has a member 'is_kmalloc' indicating whether its host
kmem_cache is a kmalloc cache.  With newly introduced is_kmalloc_cache()
helper, 'is_kmalloc' and its related function can be replaced and removed.

Also 'kasan_cache' is only needed by KASAN generic mode, and not by SW/HW
tag modes, so refine its protection macro accordingly, suggested by Andrey
Konoval.

Link: https://lkml.kernel.org/r/20230104060605.930910-2-feng.tang@intel.com
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>