staging: vt6656: correct packet types for CTS protect, mode.

It appears that the driver still transmits in CTS protect mode even
though it is not enabled in mac80211.

That is both packet types PK_TYPE_11GA and PK_TYPE_11GB both use CTS protect.
The only difference between them GA does not use B rates.

Find if only B rate in GB or GA in protect mode otherwise transmit packets
as PK_TYPE_11A.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/9c1323ff-dbb3-0eaa-43e1-9453f7390dc0@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>