wl1271: Fix scan parameter handling for 5GHz

The 5GHz bands were scanned without the proper IE's in place, preventing
proper 5GHz scanning. This patches fixes the problem by storing a pointer
to the scan request (with the IE's) for all iterations of scan.

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>