wl1271: fix a bunch of sparse warnings

A couple of sparse warnings in some rate settings (missing cpu_to_le32) were
fixed.  Changed the conf_sg_settings struct from le to native endianess.  The
values are converted to le when copying them to the acx command instead.

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