tools/mm/slabinfo: Fix trace disable logic inversion

tools/mm/slabinfo: Fix trace disable logic inversion

The disable trace path in slab_debug() had a logic error where it would
set trace=1 instead of trace=0. This made trace functionality permanently
enabled once turned on for any slab cache.

Fixes: a87615b8f9e2 ("SLUB: slabinfo upgrade")
Cc: stable@vger.kernel.org
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Xuewen Wang <wangxuewen@kylinos.cn>
WARNING: From:/Signed-off-by: email address mismatch: 'From: wangxuewen <18810879172@163.com>' != 'Signed-off-by: wangxuewen <wangxuewen@kylinos.cn>'
Link: https://patch.msgid.link/20260518062159.80664-2-wangxuewen@kylinos.cn
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>