Cleanup of free_vdev_map and vif limits.

[Ben Greear]

Just FYI, I'm planning to clean up the free_vdev_map
logic.

Currently it does not deal well with the different VIF
limits in 10X firmware and earlier.  There are several places
where the vdev counts are hard-coded, etc.

I plan to have an ar->foo variable that holds the actual
max vdevs, and make the free_vdev_map 64-bit.

I also plan to add an IE to the firmware prefix so firmware can
advertise how many vdevs and stations it can support.

Thanks,
Ben

-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com