brcmfmac: setup wiphy bands after registering it first

During bands setup we disable all channels that firmware doesn't support
in the current regulatory setup. If we do this before wiphy_register
it will result in copying set flags (including IEEE80211_CHAN_DISABLED)
to the orig_flags which is supposed to be persistent. We don't want this
as regulatory change may result in enabling some channels. We shouldn't
mess with orig_flags then (by changing them or ignoring them) so it's
better to just take care of their proper values.

This patch cleanups code a bit (by taking orig_flags more seriously) and
allows further improvements like disabling really unavailable channels.
We will need that e.g. if some frequencies should be disabled for good
due to hardware setup (design).

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>