Revert "mac80211: use a struct for bss->mesh_config"

This reverts commit 6c4711b4

.

That patch breaks mesh config comparison between beacons/probe reponses, so
every beacon from a mesh network would be added as a new bss. Since the
comparison has to be performed for every received beacon I believe it is best to
save the mesh config in a format easy to compare, rather than do a bunch of
unaligned accesses to compare field by field.

Signed-off-by: John W. Linville <linville@tuxdriver.com>