mac80211: Use setup_timer instead of init_timer

Use setup_timer() and setup_deferrable_timer() to set the data and
function timer fields. It makes the code cleaner and will allow for
easier change of the timer struct internals.

Signed-off-by: Ondřej Lysoněk <ondrej.lysonek@seznam.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: <linux-wireless@vger.kernel.org>
Cc: <netdev@vger.kernel.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>