brcmfmac: support parse country code map from DT

With any regulatory domain requests coming from either user space or
802.11 IE (Information Element), the country is coded in ISO3166
standard.  It needs to be translated to firmware country code and
revision with the mapping info in settings->country_codes table.
Support populate country_codes table by parsing the mapping from DT.

The BRCMF_BUSTYPE_SDIO bus_type check gets separated from general DT
validation, so that country code can be handled as general part rather
than SDIO bus specific one.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210417075428.2671-1-shawn.guo@linaro.org