cfg80211: extend ieee80211_operating_class_to_band() for 6GHz

Add 6GHz operating class range as defined in 802.11ax D4.1 Annex E.

Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Leon Zegers <leon.zegers@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://lore.kernel.org/r/1564745465-21234-5-git-send-email-arend.vanspriel@broadcom.com


Signed-off-by: Johannes Berg <johannes.berg@intel.com>