open80211s: Stop using zero for address 3 in mesh plink mgmt frames

Previous versions of 11s draft used the all zeroes address.  Current
draft uses the same address as address 2.

Also, use the ANA-approved action category code for peer establishment frames.

Note: This breaks compatibility with previous mesh protocol instances.

Signed-off-by: Javier Cardona <javier@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>