staging: ath6kl: Fixing key settings for WPA/WPA2

A bug was observed during the reconnection phase in the WPA/WPA2-PSK scenario
where the EAPOL frames were going encrypted during an auto reconnection
attempt. The initial 4-way handshake would go fine but then the driver
was getting a command to set default keys sometime later. Setting of an
incorrect flag (TX_USAGE) in the hadrware was causing the EAPOL frames during
the subsequent 4-way handshake attempts to go encrypted causing the AP to
reject the station.

Signed-off-by: Vipin Mehta <vmehta@atheros.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>