LinuxKPI: 802.11: fix lkpi_scan_ies_add() channel lookup

When looking up the channel we may not get a result if no flags are
passed in as net80211 channel list setup and lookup coding requires a
matching flag (band). So pass in IEEE80211_CHAN_[AG] depending on band
to increase the chances of finding a base channel and from that derive
rates, etc.

Sponsored by: The FreeBSD Foundation

(cherry picked from commit f1a110f1f0f2ef83758f7d0a984b14f512ea00fd)