mac80211: insert mesh peer after init

Drivers need the station rate info when inserting a new sta_info. The
patch "mac80211: refactor mesh peer initialization" wrongly assumed the
rate info could be applied after insertion. After further review, this
is clearly not the case.

This fixes a regression where HT parameters were not applied before
inserting the sta_info, causing performance degradation.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>