net: Remove orphaned ax25_ptr references

The AX.25 subsystem was removed in commit dd8d4bc
("net: remove ax25 and amateur radio (hamradio) subsystem"),
which removed the ax25_ptr field from struct net_device but
left behind the kdoc comment and documentation.

Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20260531134837.4111349-1-costa.shul@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: makelinux

Documentation/networking/net_cachelines/net_device.rst

@@ -91,7 +91,6 @@ struct vlan_info*                   vlan_info
 struct dsa_port*                    dsa_ptr
 struct tipc_bearer*                 tipc_ptr
 void*                               atalk_ptr
-void*                               ax25_ptr
 struct wireless_dev*                ieee80211_ptr
 struct wpan_dev*                    ieee802154_ptr
 struct mpls_dev*                    mpls_ptr

include/linux/netdevice.h

@@ -1947,7 +1947,6 @@ enum netdev_reg_state {
  *	@atalk_ptr:	AppleTalk link
  *	@ip_ptr:	IPv4 specific data
  *	@ip6_ptr:	IPv6 specific data
- *	@ax25_ptr:	AX.25 specific data
  *	@ieee80211_ptr:	IEEE 802.11 specific data, assign before registering
  *	@ieee802154_ptr: IEEE 802.15.4 low-rate Wireless Personal Area Network
  *			 device struct