mac80211: provide ieee80211_sta_eosp()

The irqsafe version ieee80211_sta_eosp_irqsafe() exists, but
drivers must not mix calls to any irqsafe/non-irqsafe function.
Both ath9k and iwlwifi, the likely first users of this interface,
use non-irqsafe RX/TX/TX status so must also use a non-irqsafe
version of this function. Since no driver uses the _irqsafe()
version, remove that.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>