wifi: nl80211: reject iftype change with mesh ID change

In the Linux kernel, the following vulnerability has been resolved: wifi: nl80211: reject iftype change with mesh ID change It's currently possible to change the mesh ID when the interface isn't yet in mesh mode, at the same time as changing it into mesh mode. This leads to an overwrite of data in the wdev->u union for the interface type it currently has, causing cfg80211_change_iface() to do wrong things when switching. We could probably allow setting an interface to mesh while setting the mesh ID at the same time by doing a different order of operations here, but realistically there's no userspace that's going to do this, so just disallow changes in iftype when setting mesh ID.