scripts/gdb: slab: update field names of struct kmem_cache

The commit 5ba6bc2 ("slab: decouple pointer to barn from
kmem_cache_node") reorganized the struct kmem_cache to factor out the
per-node fields to the new struct kmem_cache_per_node_ptrs.  This causes
the gdb scripts for lx-slabinfo and lx-slabtrace fail as they still
reference the old structure.

Adjust the gdb scripts to match the current state of struct kmem_cache.

Link: https://lore.kernel.org/20260427142448.666117-3-illia@yshyn.com
Fixes: 5ba6bc2 ("slab: decouple pointer to barn from kmem_cache_node")
Signed-off-by: Illia Ostapyshyn <illia@yshyn.com>
Acked-by: Harry Yoo (Oracle) <harry@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Florian Fainelli <florian.fainelli@broadcom.com>
Cc: Hao Li <hao.li@linux.dev>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Seongjun Hong <hsj0512@snu.ac.kr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: iostapyshyn

scripts/gdb/linux/slab.py

@@ -196,7 +196,7 @@ def process_slab(loc_track, slab_list, alloc, cache):
 
     if target_cache['flags'] & SLAB_STORE_USER:
         for i in range(0, nr_node_ids):
-            cache_node = target_cache['node'][i]
+            cache_node = target_cache['per_node']['node'][i]
             if cache_node['nr_slabs']['counter'] == 0:
                 continue
             process_slab(loc_track, cache_node['partial'], alloc, target_cache)
@@ -300,7 +300,7 @@ def count_free(slab):
         nr_free = 0
         nr_slabs = 0
         for i in range(0, nr_node_ids):
-            cache_node = cache['node'][i]
+            cache_node = cache['per_node']['node'][i]
             try:
                 nr_slabs += cache_node['nr_slabs']['counter']
                 nr_objs = int(cache_node['total_objects']['counter'])