Staging: ath6kl, remove unneeded ptr checking

In wmi_bssInfo_event_rx, there is unneeded check for bss, because it
is in the branch where the bss is checked to be non-null already.

Remove the superfluous check.

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