Use legacy NL80211 STA events for older drivers

This allows tethering on devices with older bcmdhd
drivers to be fixed.  It conditionally reverts
b638fe75d3cb9d21c67386173f10afe65053cc4d
"nl80211: Use native cfg80211 sta events" for these
boards.

Use BOARD_LEGACY_NL80211_STA_EVENTS to enable
this conditional revert.

Forward-port to JB MR1, squashed in Steve Kondik's commit
to handle additional changes.

Change-Id: I88bc4f43f35c8620ed3eeba34b0a9db2e080818c
7 files changed