ipq40xx: add DSL support for FritzBox 7530

ipq40xx: add DSL support for FritzBox 7530

Set up MAC, LED, settings and default packages for DSL usage, similar
to the lantiq target.

Due to licensing uncertainty, we do not include the firmware files for the
DSL drivers. To have a working DSL setup, follow the instructions below.

Download the firmware files locally:

  mkdir -p files/lib/firmware/09a9
  wget -P files/lib/firmware/09a9 https://gitlab.com/prpl-foundation/intel/vrx518_aca_fw/-/raw/ugw-8.5.2/platform/xrx500/aca_fw.bin
  wget -P files/lib/firmware https://gitlab.com/prpl-foundation/intel/vrx518_ppe_fw/-/raw/ugw_8.5.2.10/platform/xrx500/ppe_fw.bin
  wget -P files/lib/firmware https://gitlab.com/prpl-foundation/intel/dsl_vr11_firmware_xdsl/-/raw/ugw-8.5.2/xcpe_8D1507_8D0901.bin
  ln -s xcpe_8D1507_8D0901.bin files/lib/firmware/vdsl.bin

For people building their own images:

Run the above commands in the root of your local OpenWrt clone,
and the firmware files will be part of the resulting images.

For people downloading images:

Copy the firmware files onto the router once it's booted up:
  scp -O -r files/lib/firmware root@fritz:/lib
Reboot the device afterwards.

Signed-off-by: Martin Schiller <ms.3headeddevs@gmail.com>
[cleaned up]
Signed-off-by: Andre Heider <a.heider@gmail.com>
[set up LED]
Signed-off-by: Jan Hoffmann <jan@3e8.eu>
Signed-off-by: Andre Heider <a.heider@gmail.com>