The 5 GHz channels are stored in one hw_features set with mode
HOSTAPD_MODE_IEEE80211A while the 6 GHz channels will need to stored in
a separate hw_features set (but with same mode HOSTAPD_MODE_IEEE80211A)
due to possibility of different HE capabilities being available between
the 5 GHz and 6 GHz bands.
Search through all hw_features sets whose mode is same as the input mode
while finding channel corresponding to the input frequency in
hw_get_channel_freq().
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>