mac802154: rework sdata state change to running

This patch reworks the handling for setting the state like mac80211. We
use bit's instead a bool variable. The mutex is not needed because it use
test and set bits which are atomic operations.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>