staging: vt6656: s_nsBulkOutIoCompleteWrite fix bug of 5GHZ a rates idx

On 2GHz band the values of wCurrentRate match the idx rates.

However, on 5GHz they do not because in channel.c vnt_rates_a do not
match idx.

Instead use the info->control.rates[0].idx the value that was tried.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>