Revert "ath5k: honor FIF_BCN_PRBRESP_PROMISC in STA mode"

Unfortunately, the result was that mac80211 didn't see all the beacons
it actually wanted to see.  This caused lost associations.

Hopefully we can revisit this when mac80211 is less greedy about seeing
beacons directly...

This reverts commit 06327906

.

Signed-off-by: John W. Linville <linville@tuxdriver.com>