wl1271: Add rudimentary ad-hoc support

This patch adds rudimentary a-hoc support for the driver. It will allow
setting up ad-hoc, and for other devices to scan and join. The beacon and probe
response template setting is slightly dirty, and need to be properly
implemented with support from mac80211. Also, the SSID is not configured to the
firmware - the FW will not be able to respond to probe requests autonomously.

Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>