staging: vt6656: remove difs / sifs adjustments.

Now mac89211 is doing frame timing in rxtx these vendor adjustments need
to be removed.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Link: https://lore.kernel.org/r/034e445c-b245-52c4-c855-431b9783bcff@gmail.com


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