Bump __FreeBSD_version for net80211 'struct ieee80211vap' changes

Change 9b998db87c28 changed 'struct ieee80211vap' internals in net80211.
Given we do not have enough spares and the struct is allocated by
drivers, all wireless drivers have to be recompiled.
__FreeBSD_version is updated to 1303001 to track this change.

Approved by: re (cperciva)