armbian-firmware: new package

armbian-firmware: new package

This package enables access to firmware blobs from Armbian firmware
repository: https://github.com/armbian/firmware

That repository contains multiple firmware blobs grouped by vendor.
For the sake of convenience each group can be independently selected
using Kconfig options. This commit enables the following options:
- firmware blobs for XR819 SDIO WiFi chip
- firmware blobs for AP6212 WiFi/BT combo

Armbian firmware repository does not include any specific licenses.
Most part of those firmware blobs belongs to various Android/Linux
SDK packages provided by board vendors. As a result, this package
makes use of the following conservative approach for all the
selected firmware binaries:
  FIRMWARE_LICENSE = PROPRIETARY
  FIRMWARE_REDISTRIBUTE = NO

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>