Quantenna Pearl device exposes multiple (up to 3) radio interfaces under
single PCIe function. So far all the wiphy devices were attached to the
same pcie device. As a result, all different wireless network devices
were reported under the same sysfs directory for pcie device, e.g.:

$ ls  /sys/class/net/wlan0/device/net/
  wlan0 wlan1

It turns out that such behavior may confuse various users of wireless
subsystem. For instance, it turned out to be the case for:
- Linux init systems, e.g. for renaming based on parent device
- OpenWRT configuration scripts

Suggested solution is to add an intermediate virtual platform device
for each radio interface.
Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>