wifi: iwlwifi: mvm: add an unassign_vif_chanctx() callback for MLD mode

This is another patch in the series adding all the ops
for the new MLD ieee80211_ops.
The callback added here uses the new MLD FW API

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230314194113.5d4bcd384425.I263eef3aad8efe23a597843fe7c56924038c8fdc@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>