Staging: wlan-ng prism2usb: add suspend/resume

There is no need trying to load the (even in most cases) not availible
firmware after suspend. This saves about 30 secounds on reset waiting
for timeout.

Signed-off-by: Christoph Fritz <chf.fritz@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>