rndis_wlan: convert scan to cfg80211

Convert scan function to cfg80211. Unlike old scan code new code
waits 1 sec before getting scan data from device and passing
forward to cfg80211.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>