wifi: iwlwifi: mvm: dissolve iwl_mvm_mac_add_interface_common()

This wasn't really common anymore, so dissolve it, it has a
pretty strange calling convention that's confusing.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230524203151.44320ab2e842.Ie1d6b9c28caca3b541ca383a4c0c8799b0e72fe0@changeid


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