ipq40xx: fix compatibility with linux-atm tools

ipq40xx: fix compatibility with linux-atm tools

atm_qos struct should be the same both for user and kernel spaces. Via
the __SO_ENCODE() macro it is used to define the SO_ATMQOS socket IOC.

During the VRX518 support introduction, the atm_trafprm sturct nested
into the atm_qos stucture was update with newer fields that are
referenced by the ATM TC layer of the VRX518 TC driver. These new fields
are intended to communicate information for extra traffic classes
supported by the driver. But we are still using vanilla kernel headers
to build the toolchain. Due to the atm.h header incoherency br2684ctl
from linux-atm tools is incapable to configure the ATM bridge netdev:

  br2684ctl: Interface "dsl0" created sucessfully
  br2684ctl: Communicating over ATM 0.1.2, encapsulation: LLC
  br2684ctl: setsockopt SO_ATMQOS 22 <-- EINVAL errno
  br2684ctl: Fatal: failed to connect on socket; File descriptor in bad state

There are two options to fix this incoherency. (a) update the header
file in the toolchain to build linux-atm against updated atm_trafprm and
atm_qos structures, or (b) revert atm_trafprm changes.

Since there are no actual users of the extra ATM QoS traffic classes,
just drop these extra traffic classes from vrx518_tc ATM TC layer and
drop the kernel patch updating atm.h.

Besides fixing the compatibility with linux-atm tools, removing the
kernel patch should simplify kernel updates removing unneeded burden of
maintenance.

Run tested with FRITZ!Box 7530 with disabled extra traffic classes and
then removed them entirely before the submission.

CC: John Crispin <john@phrozen.org>
Fixes: cfd42a0098 ("ipq40xx: add Intel/Lantiq ATM hacks")
Suggested-by: Andre Heider <a.heider@gmail.com>
Reported-and-tested-by: nebibigon93@yandex.ru
Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Link: https://patchwork.ozlabs.org/project/openwrt/patch/20250122222654.21833-4-ryazanov.s.a@gmail.com/
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>