net: fib_rules: Add error_free label in fib_delrule().

We will hold RTNL just before calling fib_nl2rule_rtnl() in
fib_delrule() and release it before kfree(nlrule).

Let's add a new rule to make the following change cleaner.

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/20250207072502.87775-8-kuniyu@amazon.com


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