staging: vt6656: vnt_get_rtscts_duration_le use ieee80211_ctstoself_duration

use the mac80211 ieee80211_ctstoself_duration for CTS to self frames.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/f12b3d71-eb61-340b-e473-83509d9bc38a@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>