[PATCH] libertas: fix scanning from associate path

The previous scan fix did not account for scan paths other than set_scan()
that need to do a full scan at once.

Add a "full_scan" parameter to wlan_scan_networks() to control such
behaviour.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>