wifi: iwlwifi: mvm: remove extra link ID

wifi: iwlwifi: mvm: remove extra link ID

Since the iwlmvm driver now only supports pre-MLO devices,
we no longer need to maintain an extra explicit link ID;
valid MAC IDs and link IDs are both in the range 0-3 and
the driver always has a 1:1 MAC/link correspondence. Thus,
simply use the MAC ID as the link ID as well.

This simplifies some further work because on RX the ID is
given but there is some confusion about which versions of
the firmware report MAC and which report link ID.

While at it, clarify iwl_mvm_handle_missed_beacons_notif()
code a bit so it doesn't look like an invalid vif pointer
is being used.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20250711183056.005aa5fe34fe.Ib0c1187453f46ce49dc0f9f58907ee21f5b52634@changeid