iwlwifi: remove mac_addr assignment

priv->mac_addr is the address of the operating
interface, not the permanent MAC address. They
are usually the same, but the user can override
the operating address, so we shouldn't set the
variable to the permanent one, it is assigned
when an interface is added.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>