cw1200: prevent speculative execution

cw1200: prevent speculative execution

Since the queue value in function cw1200_conf_tx()
seems to be controllable by userspace and later on
conditionally (upon bound check) used in
WSM_TX_QUEUE_SET, insert an observable speculation
barrier before its usage. This should prevent
observable speculation on that branch and avoid
kernel memory leak.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Orabug: 27340445
CVE: CVE-2017-5753

Signed-off-by: Chuck Anderson <chuck.anderson@oracle.com>
Conflicts:
        patch refers to drivers/net/wireless/st/cw1200/sta.c
        code base has drivers/net/wireless/cw1200/sta.c

Reviewed-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Kirtikar Kashyap <kirtikar.kashyap@oracle.com>