staging: brcm80211: fixed sparse endianness warnings on fullmac scan pars

Three structures that are sent to the dongle have been annotated for correct
endianness:  struct brcmf_iscan_params, brcmf_scan_params,
brcmf_cfg80211_scan_req.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>