could you try to download following files?
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/brcm/brcmfmac43455-sdio.AW-CM256SM.txt
-> /lib/firmware/brcm/brcmfmac43455-sdio.txt
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/cypress/cyfmac43455-sdio.bin
-> /lib/firmware/brcm/brcmfmac43455-sdio.bin
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/plain/cypress/cyfmac43455-sdio.clm_blob
-> /lib/firmware/brcm/brcmfmac43455-sdio.clm_blob