brcm80211: use endian annotations in scan related function

The scan related functions provide scan parameters to the device
which need to be in little-endian. These parameters have been
annotated and conversions were placed as needed.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>