Don't attempt to manually set the channel in infrastructure mode, the
firmware doesn't like that much. Also don't attempt to override the
firmware's default channel number for IBSS mode (I believe default
channel can vary by regulatory domain).
Signed-off-by: David Gibson <hermes@gibson.dropbear.id.au>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>