sctp: Don't copy sk_sndbuf and sk_rcvbuf in sctp_sock_migrate().

sctp: Don't copy sk_sndbuf and sk_rcvbuf in sctp_sock_migrate().

sctp_sock_migrate() is called from 2 places.

1) sctp_accept() calls sp->pf->create_accept_sk() before
   sctp_sock_migrate(), and sp->pf->create_accept_sk() calls
   sctp_copy_sock().

2) sctp_do_peeloff() also calls sctp_copy_sock() before
   sctp_sock_migrate().

sctp_copy_sock() copies sk_sndbuf and sk_rcvbuf from the
parent socket.

Let's not copy the two fields in sctp_sock_migrate().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/20251023231751.4168390-3-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>