LinuxKPI: 802.11: fix ieee80211_add_channel_cbw() argument

Fix the last argument passed to ieee80211_add_channel_cbw() in
lkpi_ic_getradiocaps() for both 2Ghz and 5Ghz bands.
We passed in the unmodified version rather than the adjusted version
based on the per-band channel information possibly leaving
ieee80211_channel_flags enabled which should not be.

So far this should not have made a difference given we did not enable
HT or VHT.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days
Reviewed by: cc
Differential Revision: https://reviews.freebsd.org/D42424