iwlwifi: clean up PS code

This removes all the dead code that tries to adjust the power
saving level based on the system AC state (inacceptable policy
in the kernel) or based on overtemp conditions (unused).

Also, pass _all_ policy wrt. enabling PS to mac80211, since
we do not use the power_disabled internally I now use that to
mirror the mac80211 CONF_PS setting. When mac80211 turns off
CONF_PS we follow suit. This means that the user power level
(which can currently only be set from sysfs) is not touched
for mac80211 powersave changes.

This means no "association status" checks are necessary since
mac80211 will not allow power save to be enabled when not
associated.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-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>