net-memcg: Pass struct sock to mem_cgroup_sk_(un)?charge().

We will store a flag in the lowest bit of sk->sk_memcg.

Then, we cannot pass the raw pointer to mem_cgroup_charge_skmem()
and mem_cgroup_uncharge_skmem().

Let's pass struct sock to the functions.

While at it, they are renamed to match other functions starting
with mem_cgroup_sk_.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Link: https://patch.msgid.link/20250815201712.1745332-9-kuniyu@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>