memcg_slabinfo: Fix use of PG_slab

Check PGTY_slab instead of PG_slab.

Fixes: 4ffca5a (mm: support only one page_type per page)
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20250611155916.2579160-11-willy@infradead.org
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: Matthew Wilcox (Oracle)

tools/cgroup/memcg_slabinfo.py

@@ -146,11 +146,11 @@ def detect_kernel_config():
 
 
 def for_each_slab(prog):
-    PGSlab = ~prog.constant('PG_slab')
+    slabtype = prog.constant('PGTY_slab')
 
     for page in for_each_page(prog):
         try:
-            if page.page_type.value_() == PGSlab:
+            if (page.page_type.value_() >> 24) == slabtype:
                 yield cast('struct slab *', page)
         except FaultError:
             pass