iwl3945: Fix iwl3945 rate scaling.

3945 rate scaling was broken in recent tree. This patch fix the following:
	1- Get TX response info and update rates window.
	2- Rate scaling selection.
	3- Flush window timer.

Signed-off-by: Mohamed Abbas <mohamed.abbas@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>