brcmfmac: use ISO3166 country code and 0 rev as fallback

Instead of aborting country code setup in firmware, use ISO3166 country
code and 0 rev as fallback, when country_codes mapping table is not
configured.  This fallback saves the country_codes table setup for recent
brcmfmac chipsets/firmwares, which just use ISO3166 code and require no
revision number.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210425110200.3050-1-shawn.guo@linaro.org