net: rsi: mac80211: constify ieee80211_ops

ieee80211_ops are not supposed to change at runtime. All functions
working with ieee80211_ops provided by <net/mac80211.h> work with
const ieee80211_ops. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>