mac80211: remove max_bandwidth

This removes the max_bandwidth attribute.  It is only ever
written to, and is duplicated by max_bandwidth_khz in the
regulatory code.

Signed-off-by: Pat Erley <pat-lkml@erley.org>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>