iwl3945: disable power save

we see from http://bugzilla.intellinuxwireless.org/show_bug.cgi?id=2125
that power saving does not work well on 3945. Since then power saving has
also been connected with association problems where an AP deathenticates a
3945 after it is unable to transmit data to it - this happens when 3945
enters power savings mode.

Disable power save support until issues are resolved.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
CC: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>