cfg80211: adapt to new channelization of the 6GHz band

The 6GHz band does not have regulatory approval yet, but things are
moving forward. However, that has led to a change in the channelization
of the 6GHz band which has been accepted in the 11ax specification. It
also fixes a missing MHZ_TO_KHZ() macro for 6GHz channels while at it.

This change is primarily thrown in to discuss how to deal with it.
I noticed ath11k adding 6G support with old channelization and ditto
for iw. It probably involves changes in hostapd as well.

Cc: Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>
Cc: Jouni Malinen <jouni@w1.fi>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://lore.kernel.org/r/edf07cdd-ad15-4012-3afd-d8b961a80b69@broadcom.comSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/util.c

@@ -92,9 +92,11 @@ u32 ieee80211_channel_to_freq_khz(int chan, enum nl80211_band band)
 			return MHZ_TO_KHZ(5000 + chan * 5);
 		break;
 	case NL80211_BAND_6GHZ:
-		/* see 802.11ax D4.1 27.3.22.2 */
+		/* see 802.11ax D6.1 27.3.23.2 */
+		if (chan == 2)
+			return MHZ_TO_KHZ(5935);
 		if (chan <= 253)
-			return MHZ_TO_KHZ(5940 + chan * 5);
+			return MHZ_TO_KHZ(5950 + chan * 5);
 		break;
 	case NL80211_BAND_60GHZ:
 		if (chan < 7)