[brcmfmac] Fix regulatory domain handling to reset bands properly

[dberlin]

Currently, we ignore the default country in the reg notifier. We also register a custom regulatory domain, which is set as the default. As a result, the chip is likely to be set to the correct country, but the regulatory domain will not match it.

When the regulatory notifier is then called, we see the countries are the same and do not change anything, even though the domain is wrong.

This patch forces us to reset the bands on the first country change even if the chip is already set to that country.

We also restore the original band info before reconstructing channel info, as the new regdom power limits may be higher than what is currently set.

Without this patch, we are stuck in the custom regulatory domain the driver defines, which are very low (20dbm vs 30dbm).

[dberlin]

Here's a before/after for channels https://gist.github.com/dberlin/ee03679b6a6e93395219de2034f1c4db

[marcan]

Manually cherry-picked, thanks!