rtlwifi: rtl8192cu: Fix incorrect signal strength for unassociated AP

rtlwifi: rtl8192cu: Fix incorrect signal strength for unassociated AP

commit 78dbfecb95be4635b995af3bd29fa10013409fcd upstream.

The routine that processes received frames was returning the RSSI value for the
signal strength; however, that value is available only for associated APs. As
a result, the strength was the absurd value of 10 dBm. As a result, scans
return incorrect values for the strength, which causes unwanted attempts to roam.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>