Set correct tx width

tx width must be set to 0 if only 20MHz is supported.
1 in case 20/40MHz supported.

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>
Configure secondary channel offset

Keys exchange always fails on 5GHz with 40MHz channel
because extension channel was not set to secondary channel
offset.

Signed-off-by: Eugene Krasnikov <k.eugene.e@gmail.com>