Staging: add wlan-ng prism2 usb driver

This adds the wlan-ng prism2 USB driver to the drivers/staging tree.

The code was originally written by the linux-wlan-ng team, patched by
some Novell engineers to properly work on newer kernels, and then hacked
into place in order to get it to build properly in a single subdirectory
within the kernel tree by me.

It supports a wide range of older USB prism2 devices, and contains a
80211 stack to support this single driver.

Cc: Christian Zoz <zoz@suse.de>
Cc: Andreas Gruenbacher <agruen@suse.de>
Cc: linux-wireless <linux-wireless@vger.kernel.org>
Cc: John Linville <linville@tuxdriver.com>
Cc: Helmut Schaa <helmut.schaa@googlemail.com>
Cc: linux-wlan-ng <solomon@linux-wlan.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>