staging: brcm80211: remove the rest of broadcom specific byte swapping routines

- move ltoh16_buf/htol16_buf util/bcmsrom.c
- replace ltoh16_buf in brcmsmac/wlc_mac80211.c with several
  le16_to_cpu's

Signed-off-by: Stanislav Fomichev <kernel@fomichev.me>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>