mac80211: update mesh peer link counter during userspace peering

The established peer link count is indicated in mesh beacons and
used for other internal tasks. Previously it was not updated when
authenticated peering is performed in userspace.

Signed-off-by: Marco Porsch <marco@cozybit.com>
Acked-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>