Revert "UPSTREAM: wifi: cfg80211: rename UHB to 6 GHz"

This reverts commit 9225bb80.

The regulatory type validation patches cause connection issues with
AFC/LPI APs which use regulatory type as "4".

Bug: 397869489
Bug: 442718470
Change-Id: I05e5c96912816ceffccc608eff45e6fe877561ee
Signed-off-by: Ken Sun <kensun@google.com>
[cmllamas: fix trivial conflicts in net/wireless/scan.c]
Signed-off-by: Carlos Llamas <cmllamas@google.com>