nl80211: bounce scan request back to userspace

When a scan finishes only the program that asked for it
knows what kind of scan it was; let's tell everybody else
about the scan parameters as well so they can evaluate
the result of the scan better. Also helps with debugging.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>