Output signal strength information as part of iwlist scan - before it did
not output any signal strength related information.

Signed-off-by: Holden Karau <holden@pigscanfly.ca>
Cc: Jean Tourrilhes <jt@hpl.hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>