net: fib_rules: Don't check net in rule_exists() and rule_find().

fib_nl_newrule() / fib_nl_delrule() looks up struct fib_rules_ops
in sock_net(skb->sk) and calls rule_exists() / rule_find() respectively.

fib_nl_newrule() creates a new rule and links it to the found ops, so
struct fib_rule never belongs to a different netns's ops->rules_list.

Let's remove redundant netns check in rule_exists() and rule_find().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Tested-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250207072502.87775-2-kuniyu@amazon.com


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