Comment 4 for bug 1912905

Due to a missing brcmfmac43455-sdio.raspberrypi,4-compute-module.txt alias in linux-firmware-raspi2. The CM4's we'd encountered so far (and which had been tested for WiFi compatibility were all requesting brcmfmac43456-sdio.raspberrypi,4-compute-module.txt (note 43455 vs 43456) but it appears there's a couple of board revisions out there. I'll add the necessary alias in linux-firmware-raspi2 for hirsute, then we can see about SRU'ing this.