wl12xx: Don't filter beacons that include changed HT IEs

This patch adds a beacon filter rule to pass up the beacons that
contain changed HT information elements.  These beacons need to be
passed to mac80211 so that it can act on such changes.

[Reworded commit log -- Luca.]

Signed-off-by: Shahar Levi <shahar_levi@ti.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>