[brcmfmac] Add support for 6G bands and HE

This patch adds support for 6G bands, along with HE capabilities,
as they are required to register 6G bands with wiphy.
This in turn, enables 802.11ax support for the other bands.

Scanning is not updated in this patch, so the bands are unused
except to be able to process what the firmware tells us.

Existing code is updated to handle all the bands rather than just 2g and
5g channels.

Signed-off-by: Daniel Berlin <dberlin@dberlin.org>

Author: dberlin