brcmfmac_sdio-firmware-rpi: Consolidate firmware files

[MilhouseVH]

Currently we install:

BCM43430A1.hcd from brcmfmac_sdio-firmware-rpi
brcmfmac43430-sdio.bin from kernel-firmware
brcmfmac43430-sdio.txt from wlan-firmware

This is crazy, particularly as we need to install updated brcmfmac43430-sdio.{bin,txt} (see here) but pulling the files from kernel-firmware (a repo not under our control) means that is more difficult to do - yes, we could binary patch it...

Now, all three files will be installed from brcmfmac_sdio-firmware-rpi.

This PR depends on LibreELEC/wlan-firmware#4 (I'll update this once it is merged).

The change to kernel-firmware is a hack, but the best I could think of right now.

If any non-RPi0/RPi3 platforms require brcmfmac43430-sdio.{bin,txt} then this PR is wrong, as we will only be installing these files for RPi/RPi2.

This can be backported to libreelec-8.2.

[MilhouseVH]

A second option would be to leave wlan-firmware as it is and apply the same hack I used in kernel-firmware to wlan-firmware as well, but in both cases add a condition so that we only remove the brcmfmac43430-sdio.* files if the build includes brcmfmac_sdio-firmware-rpi firmware (ie. check $FIRMWARE), ie.

if [ -n "$(echo "$FIRMWARE" | grep brcmfmac_sdio-firmware-rpi ]; then
  rm -fr $FW_TARGET_DIR/brcm/brcmfmac43430-sdio.bin
fi

and a similar change to wlan-firmware.

That way, we continue to install brcmfmac43430-sdio.{bin,txt} from wlan-firmware and kernel-firmware unless we are installing brcmfmac_sdio-firmware-rpi which installs different (newer) versions of the files.

A third option would be to add all 3 brcmfmac_sdio-firmware-rpi firmware files to wlan-firmware, and use the kernel-firmware hack. Only problem then is that if wlan-firmware were not installed for any reason, the brcmfmac_sdio-firmware-rpi package will be "broken".