(split) Replace the homegrown implementation of nitems() with calls to nitems()
(param.h).

Operating systems that don't have nitems() can easily define it on their own
net80211 OS-specific header file.

Discussed with:		adrian
reference correct cipher value in run_key_set_cb()
reference correct params in run_wme_update_cb()
correct RSSI value calculation
use ieee80211_init_channels() for all modes
add Rx err counter
(split) Add support for DLINK DWA-127 Wireless Adapter

Approved by:	cognet (mentor)
(split) Merge subtree 'usb-wlan' (commit 'b43fb423')
Merge subtree 'usb-wlan' (commit 'b43fb423')
Split 'sys/dev/usb/wlan/' into commit 'fc7f078a23e07361049a52171b9df6bcf7a92736'

git-subtree-dir: sys/dev/usb/wlan
git-subtree-mainline: 9e45d62a126745d428eb7957ab7ef18bfff7c612
git-subtree-split: fc7f078a23e07361049a52171b9df6bcf7a92736