mac80211: deinline drv_sta_state

With this .config: http://busybox.net/~vda/kernel_config

,
after deinlining the function size is 3132 bytes and there are
7 callsites.

Total size reduction: about 20 kbytes.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
CC: John Linville <linville@tuxdriver.com>
CC: Michal Kazior <michal.kazior@tieto.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
CC: linux-kernel@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>