mac80211: set HT capabilities for mesh peer

Set peer's HT capabilities, and disallow peering if we're on a different
channel type.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: Ashok Nagarajan <anagar6@uic.edu>
Signed-off-by: John W. Linville <linville@tuxdriver.com>