Bug#821400: brcmfmac_sdio should read its configs from efi vars, where applicable

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

Over in https://bugs.debian.org/821400, Ben Hutchings makes the
reasonable suggestion that where possible, when
brcm/brcmfmac43340-sdio.txt (or configuration file for other brcm
chipsets) is not available, brcmfmac_sdio should try looking for
configuration in the efi variables directly.

That would certainly make the common use case much simpler, which would
make the devices easier to use.

This is an attempt to report this suggestion upstream where it has a
chance of being implemented.  Feel free to redirect me if you think it
should be posted elsewhere.

Regards,

         --dkg