(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
(split) Add support for DLINK DWA-127 Wireless Adapter

Approved by:	cognet (mentor)
(split) Merge subtree 'usb-wlan' (commit 'b43fb423')