wl1251: create a copy of wl12xx_80211.h for wl1251

In preparation of moving wl1251 out from drivers/net/wireless/wl12xx
create a separate copy of wl12xx_80211.h.

This file should not even exist, we should instead use generic ieee80211
definitions. This will be fixed in the future so that the file can
be removed.

Signed-off-by: Kalle Valo <kvalo@adurom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>