memcg: no irq disable for memcg stock lock

There is no need to disable irqs to use memcg per-cpu stock, so let's just
not do that.  One consequence of this change is if the kernel while in
task context has the memcg stock lock and that cpu got interrupted.  The
memcg charges on that cpu in the irq context will take the slow path of
memcg charging.  However that should be super rare and should be fine in
general.

Link: https://lkml.kernel.org/r/20250506225533.2580386-5-shakeel.butt@linux.dev


Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Eric Dumaze <edumazet@google.com>
Cc: Jakub Kacinski <kuba@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>