LinuxKPI: 802.11: adjust code to new structure layout

With past commits new structures were added. Now switch over some
bss_conf fields into vif->cfg where they got moved to and remove the
old fields. This allows drivers to find the expected values in the
now expected places and work better.

Sponsored by: The FreeBSD Foundation

(cherry picked from commit 616e13301bcf274b007f84ef99ea857a55bef46d)